Table 1.

Overview of subgroup effect sizes and heterogeneity for study characteristics.

Moderator	Subgroup	k	Hedges’ g	95% CI	Q	p
Study aim	Increasing adherence	28	0.44	0.25–0.62	1.34	.25
	Improving health	15	0.25	−0.001 to 0.51
Sample	General	8	0.43	0.08–0.78	0.17	.92
	Risk group	17	0.38	0.14–0.63
	Difficulties’ group	18	0.34	0.11–0.58
Control group	Waiting list	6	0.13	−0.25 to 0.52	5.52	.06
	Standard care	28	0.33	0.14–0.51
	Active control group	9	0.71	0.37–1.04
Measure type	Self-report	21	0.19	−0.02 to 0.39	8.65	.01*
	Monitoring device	19	0.49	0.28–0.71
	Pill count	3	0.97	0.41–1.53
Recall period	≤14 days	11	0.13	−0.16 to 0.42	6.52	.04*
	>14 days	10	0.25	−0.05 to 0.54
	No recall	22	0.55	0.35–0.75
Location	United States	35	0.32	0.16–0.49	2.09	.15
	Other	8	0.61	0.26–0.95

CI: confidence interval; k: number of studies; Q: between-group Q.

^*p < .05.