Model outcome	Effect	Estimate	SE	95% CI	P value
Physical function	TNDE	−0.54	0.59	−1.60 to 0.72	0.494
	TNIE	−1.66	0.34	−2.23 to −0.96	<0.001
	Total effect	−2.21	0.62	−3.13 to −0.77	<0.001
	Proportion mediated	0.77	3.68	0.43 to 2.00	0.006

Fatigue	TNDE	−1.01	0.80	−2.73 to 0.43	0.158
	TNIE	−1.62	0.39	−2.37 to −0.85	<0.001
	Total effect	−2.63	0.82	−4.29 to −1.05	0.004
	Proportion mediated	0.62	1.09	0.30 to 1.65	0.002

Sleep disturbance	TNDE	−1.15	0.67	−2.13 to 0.45	0.204
	TNIE	−1.11	0.29	−1.90 to −0.74	<0.001
	Total effect	−2.26	0.66	−3.36 to −0.87	0.006
	Proportion mediated	0.49	3.42	0.31 to 1.49	0.008

Social roles	TNDE	−0.49	0.73	−1.88 to 0.96	0.548
	TNIE	−1.94	0.43	−2.97 to −1.32	<0.001
	Total effect	−2.43	0.78	−4.06 to −1.12	<0.001
	Proportion mediated	0.81	0.71	0.50 to 1.97	0.004

Physical function and social roles are transformed to make a higher score a worse outcome, consistent with other PROMIS-29 measures. A negative effect estimate favours the usual medical care plus chiropractic care treatment arm over the usual medical care alone arm.
PROMIS = Patient-Reported Outcomes Measurement Information System
TNDE = total natural direct effect;
TNIE = total natural indirect effect

Table 2. Total, natural direct and natural indirect effects occurring through pain interference and pain intensity of chiropractic care on physical function, fatigue, sleep disturbance and social roles.