Table 2.

Results of moderator analyses at post-intervention assessment.

	Mental distress		Positive mental health		Resilience factors
	n/k	M(SMD) [95% CI], p	n/k	M(SMD) [95% CI], p	n/k	M(SMD) [95% CI], p
Sociodemographic characteristics
Mean age	74/132	QM(1) = 1.98, p = 0.164	69/110	QM(1) = 1.67, p = .0.201	40/57	QM(1) = 0.00, p = 0.950
Gender (% women)	82/144	QM(1) = 0.00, p = 0.978	74/121	QM(1) = 0.17, p = .0.681	42/59	QM(1) = 0.49, p = 0.486
Population type (Military vs. University/College vs. Workplace)
Omnibus moderator test	55/98	QM(2) = 1.88, p = 0.163	47/72	QM(1) = 0.06, p = 0.811	32/41	QM(1) = 0.46, p = 0.638
Delivery format (eHealth vs. mHealth vs. mixed)
Omnibus moderator test	85/150	QM(2) = 2.18, p = 0.120	77/123	QM(2) = 2.27, p = 0.111	45/64	QM(1) = 1.51, p = 0.233
Theoretical foundation (CBT vs. Coping Literature vs. Mindfulness vs. Positive Psychology vs. mixed)
Omnibus moderator test	56/101	QM(4) = 1.19, p = 0.329	56/95	QM(4) = 0.50, p = 0.734	37/56	QM(4) = 0.84, p = .511
Guidance
Unguided						0.24 [0.16, 0.34], p < 0.001
Guided						0.44 [0.25, 0.64], p < 0.001
Omnibus moderator test	84/148	QM(1) = 0.95, p = 0.332	77/123	QM(1) = 2.72, p = 0.103	45/64	QM(1) = 3.81, p = 0.058
Intervention type (standalone vs. blended interventions)
Omnibus moderator test	84/149	QM(1) = 0.26, p = 0.610	76/122	QM(1) = 0.02, p = 0.897	45/64	QM(1) = 0.20, p = 0.653
Degree of individualization (individualized vs. standardized)
Omnibus moderator test	85/150	QM(1) = 2.43, p = 0.123	77/123	QM(1) = 2.25, p = 0.138	45/64	QM(1) = 0.09, p = 0.769
Intervention intensity
in weeks	82/142	QM(1) = 0.12, p = 0.729	77/123	QM(1) = 0.98, p = 0.325	45/64	QM(1) = 1.71, p = 0.198
Improvement over time
Publication year	85/150	QM(1) = 0.86, p = 0.355	77/123	QM(1) = 3.23, p = 0.076	45/64	QM(1) = 0.39, p = 0.538
Type of control group
No intervention/ waitlist		–0.30 [–0.39, –0.21], p < 0.001		0.38 [0.15, 0.60], p = 0.001
Low-intensity active control		–0.31 [–0.45, –0.17], p < 0.001		0.22 [0.04, 0.40], p = 0.019
High-intensity active control		–0.08 [–0.18, 0.01], p = 0.086		0.07 [–0.01, 0.15], p = 0.102
Omnibus moderator test	85/150	QM(2) = 6.51, p = 0.002*	77/123	QM(2) = 4.16, p = 0.019*	45/64	QM(2) = 0.18, p = 0.835
COVID-19 context (before COVID-19 vs. during COVID-19)
Omnibus moderator test	85/150	QM(1) = 0.49, p = 0.488	77/123	QM(1) = 1.12, p = 0.293	45/64	QM(1) = 0.09, p = 0.763
Small digital component (small digital component vs. other)
Omnibus moderator test	84/149	QM(1) = 0.51, p = 0.479	76/122	QM(1) = 0.18, p = 0.675	45/64	QM(1) = 0.22, p = 0.641

Note. As results were at high risk of being biased by single studies, we did not report on moderation tests when three or less effect estimates were available per subgroup.

QM(df) omnibus test for moderators, which follows approximately a χ² distribution, df degrees of freedom, k number of effect estimates, SMD standardized mean difference, p value, 95% CI 95% confidence interval.

* highlights significant results at p < .05.