Is the Placebo Powerless? —
Comparing Placebo with No Treatment

This section was compiled by Frank M. Painter, D.C.
Send all comments or additions to:

FROM:   New England Journal of Medicine 2001 (May 24); 344 (21): 1594–1602 ~ FULL TEXT


Asbjørn Hróbjartsson, M.D., and Peter C. Gøtzsche, M.D.

Department of Medical Philosophy and Clinical Theory,
University of Copenhagen,
Panum Institute, and the Nordic Cochrane Centre,
Rigshospitalet, Denmark.

BACKGROUND:   Placebo treatments have been reported to help patients with many diseases, but the quality of the evidence supporting this finding has not been rigorously evaluated.

METHODS:   We conducted a systematic review of clinical trials in which patients were randomly assigned to either placebo or no treatment. A placebo could be pharmacologic (e.g., a tablet), physical (e.g., a manipulation), or psychological (e.g., a conversation).

RESULTS:   We identified 130 trials that met our inclusion criteria. After the exclusion of 16 trials without relevant data on outcomes, there were 32 with binary outcomes (involving 3795 patients, with a median of 51 patients per trial) and 82 with continuous outcomes (involving 4730 patients, with a median of 27 patients per trial). As compared with no treatment, placebo had no significant effect on binary outcomes (pooled relative risk of an unwanted outcome with placebo, 0.95; 95 percent confidence interval, 0.88 to 1.02), regardless of whether these outcomes were subjective or objective. For the trials with continuous outcomes, placebo had a beneficial effect (pooled standardized mean difference in the value for an unwanted outcome between the placebo and untreated groups, –0.28; 95 percent confidence interval, –0.38 to –0.19), but the effect decreased with increasing sample size, indicating a possible bias related to the effects of small trials. The pooled standardized mean difference was significant for the trials with subjective outcomes (–0.36; 95 percent confidence interval, –0.47 to –0.25) but not for those with objective outcomes. In 27 trials involving the treatment of pain, placebo had a beneficial effect (–0.27; 95 percent confidence interval, –0.40 to –0.15). This corresponded to a reduction in the intensity of pain of 6.5 mm on a 100–mm visual-analogue scale.

CONCLUSIONS:   We found little evidence in general that placebos had powerful clinical effects. Although placebos had no significant effects on objective or binary outcomes, they had possible small benefits in studies with continuous subjective outcomes and for the treatment of pain. Outside the setting of clinical trials, there is no justification for the use of placebos.

From the FULL TEXT Article:


Placebos have been reported to improve subjective and objective outcomes in up to 30 to 40 percent of patients with a wide range of clinical conditions, such as pain, asthma, high blood pressure, and even myocardial infarction. [1–3] In his 1955 article "The Powerful Placebo," Beecher concluded, "It is evident that placebos have a high degree of therapeutic effectiveness in treating subjective responses, decided improvement, interpreted under the unknowns technique as a real therapeutic effect, being produced in 35.2 ± 2.2% of cases." [1]

Beecher's article and the 35 percent figure are often cited as evidence that a placebo can be an important medical treatment. The vast majority of reports on placebos, including Beecher's article, have estimated the effect of placebo as the difference from base line in the condition of patients in the placebo group of a randomized trial after treatment. With this approach, the effect of placebo cannot be distinguished from the natural course of the disease, regression to the mean, and the effects of other factors. [4–6] The reported large effects of placebo could therefore, at least in part, be artifacts of inadequate research methods.

Despite the reservations of many physicians, [7] the clinical use of placebo has been advocated in editorials and articles in leading journals. [3, 8, 9] To understand better the effects of placebo as a treatment, we conducted a systematic review of clinical trials in which patients with various clinical conditions were randomly assigned to placebo or to no treatment. We were primarily interested in the clinical effect of placebo as a treatment for disease, rather than the role of placebo as a comparison treatment in clinical trials. A secondary aim was to study whether the effect of placebo differed for subjective and objective outcomes.


      Definition of Placebo

Placebo is difficult to define satisfactorily. [5] In clinical trials, placebos are generally control treatments with a similar appearance to the study treatments but without their specific activity. We therefore defined placebo practically as an intervention labeled as such in the report of a clinical trial.

      Literature Search

We searched , EMBASE, PsycLIT, Biological Abstracts, and the Cochrane Controlled Trials Register for trials published before the end of 1998. The search was developed iteratively for synonyms of "placebo," "no treatment," and "randomized clinical trial" (the exact search strategy is available as Supplementary Appendix 1 with the full text of this article at and was based on a published protoco [110]). We systematically read the reference lists of included trials and selected books and review articles. We also asked researchers in the field to provide lists of relevant trials.

      Selection of Studies

We included studies if patients were assigned randomly to a placebo group or an untreated group (often there was also a third group that received active treatment). We excluded studies if randomization was clearly not concealed — that is, if group assignment were predictable [11] (e.g., patients were assigned to treatment groups according to the day of the month). We also excluded studies if participants were paid or were healthy volunteers, if the person who assessed objective outcomes was aware of group assignments, if the dropout rate exceeded 50 percent, or if it was very likely that the alleged placebo had a clinical effect not associated with the treatment ritual alone (e.g., movement techniques for postoperative pain). All potentially eligible trial reports were read in full by both authors. Disagreements concerning eligibility were resolved by discussion.

      Extraction of Data

Data were extracted from the report of each trial with the use of forms tested in pilot studies. We contacted the authors of the included studies when reported outcome data were inadequate for meta-analysis. We noted how the randomization was conducted and whether the therapist responsible for the administration of placebo (as distinct from the observer) was unaware of group assignments. Furthermore, we noted the purpose of the trial, the dropout rate, whether the placebo was given in addition to the standard treatment, and whether the main outcome was clearly indicated.

We noted whether the placebo was pharmacologic (e.g., a tablet), physical (e.g., a manipulation), or psychological (e.g., a conversation); whether clinical problems reported by the patients could have been observed by others (i.e., whether the symptoms were observable outcomes such as cough); and whether objective outcomes were laboratory data, were derived from examinations that required the cooperation of the patients (i.e., objective outcomes such as forced expiratory volume), or did not require such cooperation (e.g., edema).

Both reviewers independently selected outcomes by referring only to the methods sections of articles; any disagreements were resolved by discussion. As the primary outcome, we selected the main objective or subjective outcome of each trial (preferably a characteristic symptom). If a main outcome was not indicated, we used the outcome that we felt was most relevant to patients. Binary outcomes (e.g., the proportions of smokers and nonsmokers) were preferred to continuous ones (e.g., the mean number of cigarettes smoked). Data recorded immediately after the end of treatment were preferred to follow-up data, although end-of-treatment data were not always available. For crossover trials, we extracted data from the first treatment period only; if that was not possible, we used the summary data as if they had been derived from a parallel-group trial (i.e., using the between-group standard deviations and total number of participants for both groups).

      Synthesis of Data

For each trial with binary outcomes, we calculated the relative risk of an unwanted outcome, defined as the ratio of the number of patients with an unwanted outcome to the total number of patients in the placebo group, divided by the same ratio in the untreated group. Thus, a relative risk below 1.0 indicates a beneficial effect of placebo.

For trials with continuous outcomes, we calculated the standardized mean difference, which was defined as the difference between the mean value for an unwanted outcome in the placebo group and the corresponding mean value in the untreated group divided by the pooled standard deviation. [12] A value of –1 signifies that the mean in the placebo group was 1 SD below the mean in the untreated group, indicating a beneficial effect of placebo.

We calculated the pooled relative risk of an unwanted outcome for trials with binary outcomes and the pooled standardized mean difference for those with continuous outcomes. [13] Because of the different clinical conditions and settings, we expected that the data sets would be heterogeneous — that is, that the effects of individual trials would vary more than expected by chance alone. The variance and statistical significance of the differences were therefore assessed with the use of random-effect calculations. [13] We calculated the pooled effects for subjective and objective outcomes and for specific clinical problems that had been investigated in at least three trials by different research groups. [14]

We performed preplanned analyses of subgroups to see whether our findings were sensitive to the type of placebo or the type of outcome involved. Furthermore, for each trial, we plotted the effect against the inverse of its standard error (which increases with the number of trial participants). Since the variation in the estimated effect decreases with increasing sample size, the plot is expected to resemble a symmetrical funnel. If there is significant asymmetry in such funnel plots, it is usually caused by small trials' reporting greater effects, on average, than large trials, which can reflect publication bias [15] or other biases. We also performed several preplanned sensitivity analyses to determine whether our findings were sensitive to variations in the quality of the trials.

In trials with continuous outcomes, we used F tests to check whether the standard deviations of the placebo group and the untreated group were significantly different. [16] We regarded the distributions of either group as non-Gaussian if 1.64 SD exceeded the mean for positive outcomes. [17] Chi-square tests were used to test for heterogeneity on the basis of the DerSimonian and Laird Q statistic. [13, 18] Results are reported with 95 percent confidence intervals. All P values are two-tailed.


      Selection and Characteristics of Studies

We identified 727 potentially eligible trials. We subsequently excluded 597 trials for the following reasons: 404 were nonclinical or nonrandomized, 129 were missing a placebo group or an untreated group, 29 were reported in more than one publication, 11 had clearly unblinded assessment of objective outcomes, and 24 met other criteria for exclusion, such as dropout rates over 50 percent. No relevant outcome data were available for 16 of the remaining 130 trials. The analysis therefore included 114 trials. [19–132]

There were 10 crossover trials, of which 7 (which included a total of 182 patients) were handled as parallel trials. In 112 trials, there was a third group assigned to active treatment in addition to the placebo and the untreated groups. In 88 of these, determining the effect of placebo was not mentioned as an objective of the study. The trial reports were published in five languages between 1946 and 1998. The outcomes were binary in 32 trials [19–50] and continuous in 82. [51–132] In 76 trials, the outcome in the data we extracted was identified as a main outcome by the authors of the trials. If only patients in the placebo and untreated groups were counted, the trials with binary outcomes included 3,795 patients with a median of 51 patients per trial (interquartile range, 26 to 72), and the trials with continuous outcomes included 4,730 patients with a median of 27 patients per trial (interquartile range, 20 to 52).

Supp Appendix 2

Supp Appendix 3

The typical pharmacologic placebo was a lactose tablet. The typical physical placebo was a procedure performed with a machine that was turned off (e.g., sham transcutaneous electrical nerve stimulation). The typical psychological placebo was a nondirectional, neutral discussion between the patient and the treatment provider, referred to as an "attention placebo." No treatment typically entailed observation only or standard therapy; in the latter case, all patients in the trial received standard therapy, and the placebo was additional.

The results for the individual trials are available as Supplementary Appendix 2 and Supplementary Appendix 3 with the full text of this article at The trials investigated 40 clinical conditions: hypertension, asthma, anemia, hyperglycemia, hypercholesterolemia, seasickness, Raynaud's disease, alcohol abuse, smoking, obesity, poor oral hygiene, herpes simplex infection, bacterial infection, common cold, pain, nausea, ileus, infertility, cervical dilatation, labor, menopause, prostatism, depression, schizophrenia, insomnia, anxiety, phobia, compulsive nail biting, mental handicap, marital discord, stress related to dental treatment, orgasmic difficulties, fecal soiling, enuresis, epilepsy, Parkinson's disease, Alzheimer's disease, attention-deficit–hyperactivity disorder, carpal tunnel syndrome, and undiagnosed ailments.

      Binary Outcomes

Table 1

As compared with no treatment, placebo did not have a significant effect on binary outcomes (overall pooled relative risk of an unwanted outcome with placebo, 0.95; 95 percent confidence interval, 0.88 to 1.02). The pooled relative risk was 0.95 for trials with subjective outcomes (95 percent confidence interval, 0.86 to 1.05) and 0.91 for trials with objective outcomes (95 percent confidence interval, 0.80 to 1.04) (Table 1).

There was significant heterogeneity among the trials with binary outcomes (P=0.003), indicating that the variation in the effect of placebo among trials was larger than would be expected to result from chance alone. The heterogeneity was not due to small trials' showing more pronounced effects of placebo than large trials (P=0.56). [15]

Table 2

Three clinical problems had been investigated in at least three independent trials with binary outcomes: nausea, relapse after the cessation of smoking, and depression. Placebo had no significant effect on these outcomes, but the confidence intervals were wide (Table 2).

      Continuous Outcomes

The overall pooled standardized mean difference was –0.28 (95 percent confidence interval, –0.38 to –0.19). Thus, there was a beneficial effect of placebo, because the pooled mean of the placebo groups was 0.28 SD lower than the pooled mean of the untreated groups (P<0.001). The pooled standardized mean difference was significant for trials with subjective outcomes (–0.36; 95 percent confidence interval, –0.47 to –0.25) but not for trials with objective outcomes (–0.12; 95 percent confidence interval, –0.27 to 0.03) (Table 1).

There was significant heterogeneity among the trials with continuous outcomes (P<0.001). The magnitude of the effect of placebo decreased with increasing sample size (P=0.05), indicating a possible bias related to the effects of small trials.

Pain, obesity, asthma, hypertension, insomnia, and anxiety were each investigated in at least three independent trials. Only the 27 trials involving the treatment of pain (including a total of 1,602 patients) showed a significant effect of placebo as compared with no treatment (pooled standardized mean difference, –0.27; 95 percent confidence interval, –0.40 to –0.15). There was no significant effect of placebo on the other conditions, although the confidence intervals were wide (Table 2).

Expressing the standardized mean differences in terms of clinical outcomes indicates that the effect of placebo on pain corresponds to a reduction in the mean intensity of pain of 6.5 mm (95 percent confidence interval, 3.6 to 9.6) on a 100–mm visual-analogue scale. The nonsignificant effect of placebo on obesity corresponds to a reduction in mean weight of 3.2 percent (95 percent confidence interval, 7.4 to –1.2 percent); on hypertension, a reduction in mean diastolic blood pressure of 3.2 mm Hg (95 percent confidence interval, 7.8 to –1.3); and on insomnia, a decrease in the mean time required to fall asleep of 10 minutes (95 percent confidence interval, 25 to –5). For asthma and anxiety, the measurement scales were too variable to allow clinical interpretation of the results.

Small trials involving the treatment of pain did not have significantly greater effects than large trials (P=0.20), but the power of the test was low. [15] There was no significant heterogeneity among the nine sets of data on specific clinical problems (P>0.10), but the power of these analyses was also low.

      Sensitivity Analyses

Table 3

Table 4

The number of trials compared in the sensitivity analyses was in most cases nine or more, and they included more than 1,000 patients. There was no difference in the effect of placebo between subcategories of objective and subjective binary outcomes (Table 3). The effect of placebo among subcategories of continuous outcomes did not differ significantly, except for a negative effect of placebo in four trials with laboratory data [66, 67, 75, 76] (Table 3). For both continuous and binary outcomes, there were no significant differences among the various types of placebos (Table 4).

The effect of placebo on continuous or binary outcomes was not influenced by the dropout rate (<= 15 percent vs. > 15 percent) or by whether the observers were aware of group assignments, but only two trials with binary objective outcomes (involving 316 patients) included observers who were clearly unaware of the group assignments [39, 40] (data not shown). The effects of placebo were also unrelated to whether the care providers were unaware of the treatment type (placebo or experimental), whether placebos were given in addition to standard treatments, whether the effect of placebo was an explicit research objective, or whether we had identified the main outcome on the basis of clinical relevance (data not shown). The size of the effect in trials with clearly concealed randomization did not differ from that in other trials, but only four trials with continuous outcomes [84, 95, 97, 107] (involving 523 patients) and one with binary outcomes [40] (involving 54 patients) reported clearly concealed randomization (data not shown). For continuous outcomes, the effect was not influenced by non-Gaussian distributions in the placebo or the untreated groups (data not shown).


We did not detect a significant effect of placebo as compared with no treatment in pooled data from trials with subjective or objective binary or continuous objective outcomes. We did, however, find a significant difference between placebo and no treatment in trials with continuous subjective outcomes and in trials involving the treatment of pain.

Several types of bias may have affected our findings. Blinded evaluation of subjective outcomes was not possible in the trials we reviewed. Patients in an untreated group would know they were not being treated, and patients in a placebo group would think they had received treatment. It is difficult to distinguish between reporting bias and a true effect of placebo on subjective outcomes, since a patient may tend to try to please the investigator and report improvement when none has occurred. The fact that placebos had no significant effect on objective continuous outcomes suggests that reporting bias may have been a factor in the trials with subjective outcomes.

If patients in the untreated groups sought treatment outside the trials more often than patients in the placebo groups, the effects of placebo might be less apparent. Very few trials provided information on concomitant treatment. The risk of bias is expected to be larger in trials in which placebo is the only treatment and is not given in addition to standard therapy. We did not, however, find a difference in effect between the two types of trials.

There was some evidence that placebos had greater effects in small trials with continuous outcomes than in large trials. This could indicate that some small trials with negative outcomes have not been published or that we did not identify them. [15] It is difficult to identify relevant trials in this field; another systematic search for trials involving placebo groups versus untreated groups found only 12 studies. [133] We identified 114 trials from which the outcomes could be extracted, but 88 of these trials investigated the effect of active treatment in a third group of patients and did not explicitly study the effect of placebo. Because the publication of such trials is not directly associated with the effect of placebo, it is unlikely that the existence of unpublished trials could explain the higher effects reported in small studies.

Poor methodology in small trials could also explain the large effects of placebo. It surprised us that we found no association between measures of the quality of a trial and placebo effects. However, the statistical power of our sensitivity analyses may have been too low. Furthermore, it is possible that small trials tended to investigate clinical conditions in which placebos truly had greater effects. Thus, although we found an effect of placebos on subjective continuous outcomes, the inverse relation between trial size and effect size implies that the estimates of pooled effect should be interpreted cautiously.

It can also be difficult to interpret whether a pooled standardized mean difference is large enough to be clinically meaningful. Some individual trials reported clinically relevant effects with standardized mean differences of less than –0.6,91 but such "outlier" values may be spurious. If the possible biases we have discussed are disregarded, the pooled effect of placebo on pain corresponds to one third of the effect of nonsteroidal antiinflammatory drugs, as compared with placebo, in double-blind trials. [134] It is uncertain whether such an effect is important for patients.

Our study has other limitations. We did extensive analyses of predefined subgroups according to the type of placebo, disease, and outcome without identifying a subgroup of trials in which the effect of placebo was large. However, we cannot exclude the possibility that, in the pooling of heterogeneous trials, the existence of such a subgroup was obscured. Our conclusions are also limited to the clinical conditions and outcomes that were investigated. It should be noted that few trials reported on the quality of life or patients' well-being.

We reviewed the effect of placebos but not the effect of the patient–provider relationship. We could not rule out a psychological therapeutic effect of this relationship, which may be largely independent of any placebo intervention. [20]

Moreover, the use of placebos in blinded, randomized trials is a precaution directed against many forms of bias and not only a way of controlling for the effects of placebo. Patients who are aware of their treatment assignment may differ from unaware patients in their way of reporting beneficial and harmful effects of treatment, in their tendency to seek additional treatment outside the study, and in their risk of dropping out of the study. Furthermore, staff members who are aware of treatment assignments may differ in their use of alternative forms of care and in their assessment of outcomes. Thus, even if there was no true effect of placebo, one would expect to find differences between placebo and untreated groups because of bias associated with a lack of double-blinding.

We were unable to detect any such significant difference in trials with subjective or objective binary or continuous objective outcomes. This surprising finding can possibly be explained by our selection of trials. Since our goal was to study the clinical effect of placebos, we reduced the influence of observer bias and bias due to dropouts by excluding trials with clearly unblinded objective outcomes and by attempting to analyze post-treatment data instead of follow-up data. In addition, since most trials we included did not primarily address the effect of a placebo but, rather, evaluated that of an active treatment, our study may have underestimated bias associated with the interests of the investigators. Since the design of our review precludes estimation of the overall influence of bias due to a lack of double-blinding, our results do not imply that control groups that receive no treatment can be substituted for control groups that receive placebo without creating a risk of bias. This result is in accordance with an empirical study of 33 meta-analyses, which found that randomized trials that were not double-blinded yielded larger estimates than blinded trials, with odds ratios that were exaggerated by 17 percent. [11]

In conclusion, we found little evidence that placebos in general have powerful clinical effects. Placebos had no significant pooled effect on subjective or objective binary or continuous objective outcomes. We found significant effects of placebo on continuous subjective outcomes and for the treatment of pain but also bias related to larger effects in small trials. The use of placebo outside the aegis of a controlled, properly designed clinical trial cannot be recommended.


  1. Beecher HK. The powerful placebo. JAMA 1955;159:1602-1606

  2. Lasagna L. The placebo effect. J Allergy Clin Immunol 1986;78:161-165

  3. Brown WA. The placebo effect. Sci Am 1998;278:90-95

  4. Kienle GS, Kiene H. The powerful placebo effect: fact or fiction? J Clin Epidemiol 1997;50:1311-1318

  5. Gotzsche PC. Is there logic in the placebo? Lancet 1994;344:925-926

  6. Hrobjartsson A. The uncontrollable placebo effect. Eur J Clin Pharmacol 1996;50:345-348

  7. Rawlinson MC. Truth-telling and paternalism in the clinic: philosophical reflections on the use of placebos in medical practice. In: White L, Tursky B, Schwartz GE, eds. Placebo: theory, research, and mechanisms. New York: Guilford Press, 1985:403-18.

  8. Oh VMS. The placebo effect: can we use it better? BMJ 1994;309:69-70

  9. Chaput de Saintonge DM, Herxheimer A. Harnessing placebo effects in health care. Lancet 1994;344:995-998

  10. Hróbjartsson A, Gøtzsche PC. Placebo intervention compared with no treatment (protocol for a Cochrane review). In: The Cochrane library. No. 1. Oxford, England: Update Software, 1999 (software).

  11. Schulz KF, Chalmers I, Hayes R, Altman DG. Empirical evidence of bias: dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA 1995;273:408-412

  12. Estimation of a single effect size: parametric and nonparametric methods. In: Hedges LV, Olkin I. Statistical methods for meta-analysis. Orlando, Fla.: Academic Press, 1985:75-106.

  13. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials 1986;7:177-188

  14. Linde K, Clausius N, Ramirez G, et al. Are the clinical effects of homeopathy placebo effects? A meta-analysis of placebo-controlled trials. Lancet 1997;350:834-843[Erratum, Lancet 1998;351:220.]

  15. Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ 1997;315:629-634

  16. Comparing groups — continuous data. In: Altman DG. Practical statistics for medical research. London: Chapman and Hall, 1991:179-228.

  17. Cochrane Consumers & Communication Group. Statistical policy. In: The Cochrane library. No. 1. Oxford, England: Update Software, 1999 (software).

  18. Comparing groups — categorical data. In: Altman DG. Practical statistics for medical research. London: Chapman and Hall, 1991:229-76.

  19. Tyler DB. The influence of a placebo, body position and medication on motion sickness. Am J Physiol 1946;146:458-466

  20. Thomas KB. General practice consultations: is there any point in being positive? BMJ 1987;294:1200-1202

  21. N, Wilson MH, Mellits D, et al. Effectiveness of an antihistamine-decongestant combination for young children with the common cold: a randomized, controlled clinical trial. J Pediatr 1991;118:125-130

  22. Guglielmi RS, Roberts AH, Patterson R. Skin temperature biofeedback for Raynaud's disease: a double-blind study. Biofeedback Self Regul 1982;7:99-120

  23. Watzl H, Olbrich R, Rist F, Cohen R. Placebo-Injektionen und Alkoholkontrollen in der stationären Behandlung alkoholkranker Frauen -- eine experimentelle Untersuchung Zweier Behandlungsmerkmale. Z Klin Psychol 1986;15:333-345

  24. Wilson A, Davidson WJ, Blanchard R. Disulfiram implantation: a trial using placebo implants and two types of controls. J Stud Alcohol 1980;41:429-436

  25. Killen JD, Fortmann SP, Newman B, Varady A. Evaluation of a treatment approach combining nicotine gum with self-guided behavioral treatments for smoking relapse prevention. J Consult Clin Psychol 1990;58:85-92

  26. Malcolm RE, Sillett RW, Turner JAM, Ball KP. The use of nicotine chewing gum as an aid to stopping smoking. Psychopharmacology (Berl) 1980;70:295-296

  27. Jacobs MA, Spilken AZ, Norman MM, Wohlberg GW, Knapp PH. Interaction of personality and treatment conditions associated with success in a smoking control program. Psychosom Med 1971;33:545-556

  28. Williams JM, Hall DW. Use of single session hypnosis for smoking cessation. Addict Behav 1988;13:205-208

  29. Hyman GJ, Stanley RO, Burrows GD, Horne DJ. Treatment effectiveness of hypnosis and behaviour therapy in smoking cessation: a methodological refinement. Addict Behav 1986;11:355-365

  30. Elliott CH, Denney DR. A multiple-component treatment approach to smoking reduction. J Consult Clin Psychol 1978;46:1330-1339

  31. Faas A, Chavannes AW, van Eijk JTM, Gubbels JW. A randomized, placebo-controlled trial of exercise therapy in patients with acute low back pain. Spine 1993;18:1388-1395

  32. Walton RE, Chiappinelli J. Prophylactic penicillin: effect on posttreatment symptoms following root canal treatment of asymptomatic periapical pathosis. J Endod 1993;19:466-470

  33. McMillan CM. Transcutaneous electrical stimulation of Neiguan anti-emetic acupuncture point in controlling sickness following opioid analgesia in major orthopaedic surgery. Physiotherapy 1994;80:5-9

  34. Najningier B, Patowski W, Zieniewicz K, et al. Zofran w zapobieganiu nudnosciom i wymiotom po cholecystektomii laparoskopowej. Acta Endosc Pol 1997;7:125-128

  35. Dundee JW, Chestnutt WN, Ghaly RG, Lynas AGA. Traditional Chinese acupuncture: a potentially useful antiemetic? BMJ 1986;293:583-584

  36. Adriaanse AH, Kollee LAA, Muytjens HL, Nijhuis JG, de Haan AFJ, Eskes TKAB. Randomized study of vaginal chlorhexidine disinfection during labor to prevent vertical transmission of group B streptococci. Eur J Obstet Gynecol Reprod Biol 1995;61:135-141

  37. Harrison RF, de Louvois J, Blades M, Hurley R. Doxycycline treatment and human infertility. Lancet 1975;1:605-607

  38. Aune A, Alraek T, Huo L, Barheim A. Kan akupunktur forebygge blærekatarr hos kvinner? Tidsskr Nor Laegeforen 1998;118:1370-1372

  39. Heinzl S, Andor J. Preoperative administration of prostaglandin to avoid dilatation-induced damage in first-trimester pregnancy terminations. Gynecol Obstet Invest 1981;12:29-36

  40. Tarrier N, Yusupoff L, Kinney C, et al. Randomised controlled trial of intensive cognitive behaviour therapy for patients with chronic schizophrenia. BMJ 1998;317:303-307

  41. Whittaker CB, Hoy RM. Withdrawal of perphenazine in chronic schizophrenia. Br J Psychiatry 1963;109:422-427

  42. Frank E, Kupfer DJ, Perel JM, et al. Three-year outcomes for maintenance therapies in recurrent depression. Arch Gen Psychiatry 1990;47:1093-1099

  43. Klerman GL, Dimascio A, Weisman M, Prusoff B, Paykel ES. Treatment of depression by drugs and psychotherapy. Am J Psychiatry 1974;131:186-191

  44. Rabkin JG, McGrath PJ, Quitkin FM, Tricamo E, Stewart JW, Klein DF. Effects of pill-giving on maintenance of placebo response in patients with chronic mild depression. Am J Psychiatry 1990;147:1622-1626

  45. Roughan PA, Kunst L. Do pelvic floor exercises really improve orgasmic potential? J Sex Marital Ther 1981;7:223-229

  46. Berg I, Forsythe I, Holt P, Watts J. A controlled trial of `Senokot' in faecal soiling treated by behavioral methods. J Child Psychol Psychiatry 1983;24:543-549

  47. Blackman S, Benton AJ, Cove LM. The effect of imipramine on enuresis. Am J Psychiatry 1964;120:1194-1195

  48. Double DB, Warren GC, Evans M, Rowlands RP. Efficacy of maintenance use of anticholinergic agents. Acta Psychiatr Scand 1993;88:381-384

  49. Stransky M, Rubin A, Lava NS, Lazaro RP. Treatment of carpal tunnel syndrome with vitamin B6: a double-blind study. South Med J 1989;82:841-842

  50. Tan S, Bruni J. Cognitive-behavior therapy with adult patients with epilepsy: a controlled outcome study. Epilepsia 1986;27:225-233

  51. Antivalle M, Lattuada S, Salvaggio M, Paravicini M, Rindi M, Libretti A. Placebo effect and adaptation to noninvasive monitoring of BP. J Hum Hypertens 1990;4:633-637

  52. Bosley F, Allen TW. Stress management training for hypertensives: cognitive and physiological effects. J Behav Med 1989;12:77-89

  53. Canino E, Cardona R, Monsalve P, Acuna FP, Lopez B, Fragachan F. A behavioral treatment program as a therapy in the control of primary hypertension. Acta Cient Venez 1994;45:23-30

  54. Frankel BL, Patel DJ, Horwitz D, Friedewald WT, Gaarder KR. Treatment of hypertension with biofeedback and relaxation techniques. Psychosom Med 1978;40:276-293

  55. Rossi A, Ziacchi V, Lomanto B. The hypotensive effect of a single daily dose of labetalol: a preliminary study. Int J Clin Pharmacol Ther Toxicol 1982;20:438-445

  56. Seer P, Raeburn JM. Meditation training and essential hypertension: a methodological study. J Behav Med 1980;3:59-71

  57. Yates RG, Lamping DL, Abram NL, Wright C. Effects of chiropractic treatment on blood pressure and anxiety: a randomized, controlled trial. J Manipulative Physiol Ther 1988;11:484-488

  58. Block J. Effects of rational emotive therapy on overweight adults. Psychother Theory Res Pract 1980;17:277-280

  59. Hall RG, Hanson RW, Borden BL. Permanence of two self-managed treatments of overweight in university and community populations. J Consult Clin Psychol 1974;42:781-786

  60. Hanson RW, Borden BL, Hall SM, Hall RG. Use of programmed instruction in teaching self-management skills to overweight adults. Behav Ther 1976;7:366-373

  61. Murphy JK, Williamson DA, Buxton AE, Moody SC, Absher N, Warner M. The long-term effects of spouse involvement upon weight loss and maintenance. Behav Ther 1982;13:681-693

  62. Senediak C, Spence SH. Rapid versus gradual scheduling of therapeutic contact in a family based behavioral weight control programme for children. Behav Psychother 1985;13:265-287

  63. Godfrey S, Silverman M. Demonstration of a placebo response in asthma by means of exercise testing. J Psychosom Res 1973;17:293-297

  64. May O, Hansen NCG. Comparison of terbutaline, isotonic saline, ambient air and non-treatment in patients with reversible chronic airway obstruction. Eur Respir J 1988;1:527-530

  65. Morton AR, Fazio SM, Miller D. Efficacy of laser-acupuncture in the prevention of exercise-induced asthma. Ann Allergy 1993;70:295-298

  66. Lindholm LH, Ekbom T, Dash C, Isacsson A, Schersten B. Changes in cardiovascular risk factors by combined pharmacological and nonpharmacological strategies: the main results of the CELL Study. J Intern Med 1996;240:13-22

  67. Tuomilehto J, Voutilainen E, Huttunen J, Vinni S, Homan K. Effect of guar gum on body weight and serum lipids in hypercholesterolemic females. Acta Med Scand 1980;208:45-48

  68. Diamond L, Dockhorn RJ, Grossman J, et al. A dose-response study of the efficacy and safety of ipratropium bromide nasal spray in the treatment of the common cold. J Allergy Clin Immunol 1995;95:1139-1146

  69. Hayden FG, Diamond L, Wood PB, Korts DC, Wecker MT. Effectiveness and safety of intranasal ipratropium bromide in common colds: a randomized, double-blind, placebo-controlled trial. Ann Intern Med 1996;125:89-97

  70. Stabholz A, Shapira J, Shur D, Friedman M, Guberman R, Sela MN. Local application of sustained-release delivery system of chlorhexidine in Down's syndrome population. Clin Prev Dent 1991;13:9-14

  71. Stewart JE, Jacobs-Schoen M, Padilla MR, Maeder LA, Wolfe GR, Hartz GW. The effect of a cognitive behavioral intervention on oral hygiene. J Clin Periodontol 1991;18:219-222

  72. Sipich JF, Russell RK, Tobias LL. A comparison of covert sensitization and “nonspecific“ treatment in the modification of smoking behavior. J Behav Ther Exp Psychiatry 1974;5:201-203

  73. Spanos NP, Mondoux TJ, Burges CA. Comparison of multi-component hypnotic and non-hypnotic treatments for smoking. Contemp Hypn 1995;12:12-19

  74. Longo DJ, Clum GA, Yaeger NJ. Psychosocial treatment for recurrent genital herpes. J Consult Clin Psychol 1988;56:61-66

  75. Crosby L, Palarski VA, Cottington E, Cmolik B. Iron supplementation for acute blood loss anemia after coronary artery bypass surgery: a randomized, placebo-controlled study. Heart Lung 1994;23:493-499

  76. Karunakaran S, Hammersley MS, Morris RC, Turner RC, Holman RR. The Fasting Hyperglycaemia Study. III. Randomized controlled trial of sulfonylurea therapy in subjects with increased but not diabetic fasting plasma glucose. Metabolism 1997;46:Suppl 1:56-60

  77. Nawrocki JD, Bell TJ, Lawrence WT, Ward JP. A randomized controlled trial of transurethral microwave thermotherapy. Br J Urol 1997;79:389-393

  78. GRECHO, U292 INSERM, ARC, GREPA. Evaluation de deux produits homéopathiques sur la reprise du transit après chirurgie digestive: un essai contrôlé multicentrique. Presse Med 1989;18:59-62

  79. Nyboe Andersen A, Damm P, Tabor A, Pedersen IM, Harring M. Prevention of breast pain and milk secretion with bromocriptine after second-trimester abortion. Acta Obstet Gynecol Scand 1990;69:235-238

  80. Benedetti F, Amanzio M, Maggi G. Potentiation of placebo analgesia by proglumide. Lancet 1995;346:1231-1231

  81. Benedetti F, Amanio M, Casadio C, et al. Control of postoperative pain by transcutaneous electrical nerve stimulation after thoracic operations. Ann Thorac Surg 1997;63:773-776

  82. Chenard JR, Marchand S, Charest J, Jinxue L, Lavignolle B. Évaluation d'un traitement comportmental de la lombalgie chronique: l'école interactionelle du dos. Sci Comportement 1991;21:225-239

  83. Classen W, Feingold E, Netter P. Influence of sensory suggestibility on treatment outcome in headache patients. Neuropsychobiology 1983;10:44-47

  84. Conn IG, Marshall AH, Yadav SN, Daly JC, Jaffer M. Transcutaneous electrical nerve stimulation following appendicectomy: the placebo effect. Ann R Coll Surg Engl 1986;68:191-192

  85. Coyne P, MacMurren M, Izzo T, Kramer T. Transcutaneous electrical nerve stimulator for procedural pain associated with intravenous needlesticks. J Intraven Nurs 1995;18:263-267

  86. Forster EL, Kramer JF, Lucy SD, Scudds RA, Novick RJ. Effects of TENS on pain, medications, and pulmonary function following coronary artery bypass graft surgery. Chest 1994;106:1343-1348

  87. Frega A, Stentella P, Di Renzi F, et al. Pain evaluation during carbon dioxide laser vaporization for cervical intraepithelial neoplasia: a randomized trial. Clin Exp Obstet Gynecol 1994;21:188-191

  88. Goodenough B, Kampel L, Champion GD, et al. An investigation of the placebo effect and age-related factors in the report of needle pain from venipuncture in children. Pain 1997;72:383-391

  89. Gracely RH, Dubner R, Wolskee PJ, Deeter WR. Placebo and naloxone can alter post-surgical pain by separate mechanisms. Nature 1983;306:264-265

  90. Hargreaves A, Lander J. Use of transcutaneous electrical nerve stimulation for postoperative pain. Nurs Res 1989;38:159-161

  91. Hashish I, Harvey W, Harris M. Anti-inflammatory effects of ultrasound therapy: evidence for a major placebo effect. Br J Rheumatol 1986;25:77-81

  92. Hashish I, Hai HK, Harvey W, Feinmann C, Harris M. Reduction of postoperative pain and swelling by ultrasound treatment: a placebo effect. Pain 1988;33:303-311

  93. Helms JM. Acupuncture for the management of primary dysmenorrhea. Obstet Gynecol 1987;69:51-56

  94. Hong CZ, Chen YC, Pon CH, Yu J. Immediate effects of various physical medicine modalities on pain threshold of an active myofascial trigger point. Musculoskeletal Pain 1993;1:37-53

  95. Lander J, Fowler-Kerry S. TENS for children's procedural pain. Pain 1993;52:209-216

  96. Levine JD, Gordon NC. Influence of the method of drug administration on analgesic response. Nature 1984;312:755-756

  97. Moffett JAK, Richardson PH, Frost H, Osborn A. A placebo controlled double blind trial to evaluate the effectiveness of pulsed short wave therapy for osteoarthritic hip and knee pain. Pain 1996;67:121-127

  98. Parker JC, Smarr KL, Buckelew SP, et al. Effects of stress management on clinical outcomes in rheumatoid arthritis. Arthritis Rheum 1995;38:1807-1818

  99. Reading AE. The effects of psychological preparation on pain and recovery after minor gynaecological surgery: a preliminary report. J Clin Psychol 1982;38:504-512

  100. Rowbotham MC, Davies PS, Verkempinck C, Galer BS. Lidocaine patch: double-blind controlled study of a new treatment method for post-herpetic neuralgia. Pain 1996;65:39-44

  101. Sanders GE, Reinert O, Tepe R, Maloney P. Chiropractic adjustive manipulation on subjects with acute low back pain: visual analog pain scores and plasma beta-endorphin levels. J Manipulative Physiol Ther 1990;13:391-395

  102. Sprott H, Mennet P, Stratz T, Muller W. Wirksamkeit der Akupunktur bei Patienten mit generalisierter Tendomyopathie (Fibromyalgie). Aktuel Rheumatol 1993;18:132-135

  103. Tan S, Poser EG. Acute pain in a clinical setting: effects of cognitive-behavioural skills training. Behav Res Ther 1982;20:535-545

  104. Vlaeyen JWS, Teeken-Gruben NJG, Goossens MEJB, et al. Cognitive-educational treatment of fibromyalgia: a randomized clinical trial. I. Clinical effects. J Rheumatol 1996;23:1237-1245

  105. Wojciechowski FL. Behavioral treatment of tension headache: a contribution to controlled outcome research methodology. Gedrag Tijdschrift Voor Psychol 1984;12:16-30

  106. Hawkins PJ, Liossi C, Ewart BW, Hatria P, Kosmidis VH, Varvutsi M. Hypnotherapy for control of anticipatory nausea and vomiting in children with cancer: preliminary findings. Psychooncology 1995;4:101-106

  107. O'Brien B, Relyea MJ, Taerum T. Efficacy of P6 acupressure in the treatment of nausea and vomiting during pregnancy. Am J Obstet Gynecol 1996;174:708-715

  108. Tremeau ML, Fontanie-Ravier P, Teurnier F, Demouzon J. Protocole de maturation cervicale par acupuncture. J Gynecol Obstet Biol Reprod (Paris) 1992;21:375-380

  109. Irvin JH, Domar AD, Clark C, Zuttermeister PC, Friedman R. The effects of relaxation response training on menopausal symptoms. J Psychosom Obstet Gynaecol 1996;17:202-207

  110. Ascher LM, Turner RM. Paradoxical intention and insomnia: an experimental investigation. Behav Res Ther 1979;17:408-411

  111. Espie CA, Lindsay WR, Brooks DN, Hood EM, Turvey T. A controlled comparative investigation of psychological treatments for chronic sleep-onset insomnia. Behav Res Ther 1989;27:79-88

  112. Lick JR, Heffler D. Relaxation training and attention placebo in the treatment of severe insomnia. J Consult Clin Psychol 1977;45:153-161

  113. Nicassio P, Bootzin R. A comparison of progressive relaxation and autogenic training as treatments for insomnia. J Abnorm Psychol 1974;83:253-260

  114. Turner RM, Ascher LM. Controlled comparison of progressive relaxation, stimulus control, and paradoxical intention therapies for insomnia. J Consult Clin Psychol 1979;47:500-508

  115. Kendall PC, Williams L, Pechacek TF, Graham LE, Shisslak C, Herzoff N. Cognitive-behavioral and patient education interventions in cardiac catheterization: the Palo Alto Medical Psychology Project. J Consult Clin Psychol 1979;47:49-58

  116. Lorr M, McNair DM, Weinstein GJ, Michaux WW, Raskin A. Meprobamate and chlorpromazine in psychotherapy: same effects on anxiety and hostility of outpatients. Arch Gen Psychiatry 1961;4:381-389

  117. Macaluso AD, Connelly AM, Hayes WB, et al. Oral transmucosal fentanyl citrate for premedication in adults. Anesth Analg 1996;82:158-161

  118. Markland D, Hardy L. Anxiety, relaxation and anaesthesia for day-case surgery. Br J Clin Psychol 1993;32:493-504

  119. Rybarczyk BD, Auerbach SM. Reminiscence interviews as stress management interventions for older patients undergoing surgery. Gerontologist 1990;30:522-528

  120. Theroux MC, West DW, Corddry DH, et al. Efficacy of intranasal midazolam in facilitating suturing of lacerations in preschool children in the emergency department. Pediatrics 1993;9:624-627

  121. Lick J. Expectancy, false galvanic skin response feedback, and systematic desensitization in the modification of phobic behavior. J Consult Clin Psychol 1975;43:557-567

  122. Rosen GM, Glasgow RE, Barrera M. A controlled study to assess the clinical efficacy of totally self-administrated systematic desensitization. J Consult Clin Psychol 1976;44:208-217

  123. Fuchs CZ, Rehm LP. A self-control behavior therapy program for depression. J Consult Clin Psychol 1977;45:206-215

  124. Nandi DN, Ajmany S, Ganguli H, et al. A clinical evaluation of depressives found in a rural survey in India. Br J Psychiatry 1976;128:523-527

  125. Davidson AM, Denney DR, Elliott CH. Suppression and substitution in the treatment of nailbiting. Behav Res Ther 1980;18:1-9

  126. Bramston P, Spence SH. Behavioural versus cognitive social-skills training with intellectually-handicapped adults. Behav Res Ther 1985;23:239-246

  127. Jacobson NS. Specific and nonspecific factors in the effectiveness of a behavioral approach to the treatment of marital discord. J Consult Clin Psychol 1978;46:442-452

  128. Nocella J, Kaplan RM. Training children to cope with dental treatment. J Pediatr Psychol 1982;7:175-178

  129. Weingaertner AH. Self-administered aversive stimulation with hallucinating hospitalized schizophrenics. J Consult Clin Psychol 1971;36:422-429

  130. Crapper McLachlan DR, Dalton AJ, Kruck TPA, et al. Intramuscular desferrioxamine in patients with Alzheimer's disease. Lancet 1991;337:1304-1308[Erratum, Lancet 1991;337:1618.]

  131. Quayhagen MP, Quayhagen M, Corbeil RR, Roth P, Rodgers JA. A dyadic remediation program for care recipients with dementia. Nurs Res 1995;44:153-159

  132. Pelham WE, Murphy DA, Vannatta K, et al. Methylphenidate and attributions in boys with attention-deficit hyperactivity disorder. J Consult Clin Psychol 1992;60:282-292

  133. Ernst E, Resch KL. Concept of true and perceived placebo effects. BMJ 1995;311:551-553

  134. Gotzsche PC. Sensitivity of effect variables in rheumatoid arthritis: a meta-analysis of 130 placebo controlled NSAID trials. J Clin Epidemiol 1990;43:1313-1318[Erratum, J Clin Epidemiol 1991;44:613.]

  135. Adams HG, Benson EA, Alexander ER, Ventrer LA, Remington MA, Holmes KK. Genital herpetic infection in men and women: clinical course and effect of topical application of adenine arabinoside. J Infect Dis 1976;133:Suppl:A151-A159

  136. Banner CN, Meadows WM. Examination of the effectiveness of various treatment techniques for reducing tension. Br J Clin Psychol 1983;22:183-193

  137. Brill NQ, Koegler RR, Epstein LJ, Forgy EW. Controlled study of psychiatric outpatient treatment. Arch Gen Psychiatry 1964;10:581-595

  138. Doty DW. Role playing and incentives in the modification of the social interaction of chronic psychiatric patients. J Consult Clin Psychol 1975;43:676-682

  139. Gracely RH, Deeter WR, Wolskee PJ, et al. The effect of naloxone on multidimensional scales of postsurgical pain in nonsedated patients. Soc Neurosci Abstr 1979;5:609-609

  140. Grammer LC, Shaughnessy MA, Shaughnessy JJ, Patterson R. Asthma as a variable in a study of immunotherapy for allergic rhinitis. J Allergy Clin Immunol 1984;73:557-560

  141. Hallstrom C, Crouch G, Robsen M, Shine P. The treatment of tranquillizer dependence by propranolol. Postgrad Med J 1988;64:Suppl 2:40-44

  142. Irjala J, Kanto J, Scheinin M. Monoamine metabolite and catecholamine measurements in cerebrospinal fluid in determining the quality of the pre-operative night's sleep. Eur J Anaesthesiol 1993;10:393-396

  143. Jakes SC, Hallam RS, McKenna L, Hinchcliffe R. Group cognitive therapy for medical patients: an application to tinnitus. Cognit Ther Res 1992;16:67-82

  144. Lamazza A, Tofi A, Bolognese A, Fontana B, De Masi E, Frontespezi S. Effects of pinaverium bromide in the premedication of endoscopic retrograde cholangio-pancreatography and on motor activity of the sphincter of Oddi. Cur Med Res Opin 1986;10:280-284

  145. Levitt M, Wilson A, Bowman D, et al. Physiologic observations in a controlled clinical trial of the antiemetic effectiveness of 5, 10 and 15 mg of delta 9-tetrahydrocannabinol in cancer chemotherapy: ophthalmologic implications. J Clin Pharmacol 1981;21:Suppl 8-9:103S-109S

  146. Mussell MJ, Hartley JP. Trachea-noise biofeedback in asthma: a comparison of the effect of trachea-noise biofeedback, a bronchodilator, and no treatment on the rate of recovery from exercise- and eucapnic hyperventilation-induced asthma. Biofeedback Self Regul 1988;13:219-234

  147. Pearl D, Vander Kamp H, Olsen AL, Greenberg PD, Armitage SG. The effects of reserpine on schizophrenic patients. Am J Psychiatry 1956;112:936-936

  148. Rupert PA, Holmes DS. Effects of multiple sessions of true and placebo heart rate biofeedback training on the heart rates and anxiety levels of anxious patients during and following treatment. Psychophysiology 1978;15:582-590

  149. Sibilio JP, Andrew G, Dart D, Moore KB, Stehman VA. Treatment of chronic schizophrenia with promazine hydrochloride. AMA Arch Neurol Psychiatry 1957;78:419-424

  150. Sommerness MD, Lucero RJ, Hamlon JS, Erickson JL, Matthews R. A controlled study of reserpine on chronically disturbed patients. AMA Arch Neurol Psychiatry 1955;74:316-319

Return to PLACEBOS

Since 10-20-2018

                  © 1995–2023 ~ The Chiropractic Resource Organization ~ All Rights Reserved