Table 3.

Mediators of painACTION.com intervention effects on outcome pain severity (BPI) over time

	Full mediation model (condition, mediator, time and interaction effects) †								Intervention over time model (condition, time and interaction effects; without the mediator) ‡
	Mediating (indirect) effects over time				Intervention (direct) effects over time with mediator in the model				Intervention (total) effects over time without mediator in the model
Putative Mediator	β coefficient	p value	F-test	p value	β coefficient	p value	F-test	p value	β coefficient	p value	F-test	p value
DASS
Depression			2.40	0.0659			2.04	0.1067			4.04	0.0070
Baseline	reference				reference				reference
Post	0.0050	0.3384			0.1610	0.1051			0.2043	0.0402
3-month	0.0121	0.0437			0.0421	0.719			0.1209	0.3147
6-month	0.0159	0.0145			0.2495	0.0421			0.4102	0.0013
Anxiety			1.66	0.1730			2.78	0.0395			4.04	0.0070
Baseline	reference				reference				reference
Post	0.0099	0.1264			0.1645	0.0979			0.2043	0.0402
3-month	0.0140	0.0787			0.0614	0.6038			0.1209	0.3147
6-month	0.0159	0.0533			0.3232	0.0098			0.4102	0.0013
Stress €			3.73	0.0108			2.17	0.0900			4.04	0.0070
Baseline	reference				reference				reference
Post	0.0075	0.2099			0.1468	0.1399			0.2043	0.0402
3-month	0.0152	0.0253			0.0120	0.9185			0.1209	0.3147
6-month	0.0228	0.0013			0.2524	0.0393			0.4102	0.0013
CPCI
Coping			1.01	0.3884			4.35	0.0046			4.04	0.0070
Baseline	reference				reference				reference
Post	0.0003	0.9919			0.2100	0.0359			0.2043	0.0402
3-month	0.0225	0.4683			0.1419	0.2407			0.1209	0.3147
6-month	0.0509	0.1170			0.4330	0.0007			0.4102	0.0013
Relaxation			0.93	0.4275			4.62	0.0032			4.04	0.0070
Baseline	reference				reference				reference
Post	−0.0379	0.1864			0.2180	0.0292			0.2043	0.0402
3-month	−0.0103	0.7549			0.1648	0.177			0.1209	0.3147
6-month	0.0116	0.7366			0.4552	0.0004			0.4102	0.0013
Social			0.91	0.4374			4.48	0.0038			4.04	0.0070
Baseline	reference				reference				reference
Post	−0.0231	0.3935			0.2218	0.0272			0.2043	0.0402
3-month	0.0225	0.4669			0.1722	0.155			0.1209	0.3147
6-month	−0.0129	0.6913			0.4424	0.0005			0.4102	0.0013

BPI = Brief Pain Inventory; CPCI = Chronic Pain Coping Inventory; DASS = Depression Anxiety Stress Scale.

^†Full mediation model includes the condition, mediator, time, condition*time and mediator*time as the independent variables.

^‡Model includes only the condition over time effects i.e., condition, time and condition*time as the independent variables.

^€Statistically significant at p < 0.05.

To infer mediation, the following type III tests of effects (F-test) must be statistically significant: (1) Intervention (total) effect over time on outcome pain severity; (2) Intervention effect over time on mediator (not shown in table); (3) Mediating (indirect) effect over time on outcome pain severity in the mediation model. For example, in this table stress mediates the intervention effects on pain severity as the following tests are significant: (1) Intervention (total) effect over time on outcome pain severity (F-test = 4.04, p = 0.0070); (2) Intervention effect over time on stress (F-test = 6.32, p = 0.0003; not shown in table); (3) Mediating (indirect) effect over time on outcome pain severity in the mediation model (F-test = 3.73, p = 0.0108).