Table 3.

Mean-Weighted Effect Sizes for Cognitive Domains for Cannabis Using and Nonusing Schizophrenia Patients Defined by Lifetime Use Vs Current or Recent Use Criteria

Test	Number of Studies	SCZ + CANN	SCZ − CANN	Cohen’s d	95 % CI	z	P	Q-test, P	Bias Test
Global cognition	10	223	349	0.35	0.09 to 0.61	2.63	.009	17.13*	0.34
Lifetime	6	121	138	0.55	0.30 to 0.80	4.29	<.001	3.95
Current/recent	4	102	211	0.03	−0.30 to 0.37	0.20	.84	4.59
Attention	3	68	67	0.26	−0.08 to 0.61	1.51	.13	0.50	0.26
Processing speed	8	192	322	0.40	0.11 to 0.69	2.75	.006	14.62*	0.39
Lifetime	5	103	124	0.65	0.38 to 0.92	4.70	<.001	1.72
Current/recent	3	89	198	0.09	−0.34 to 0.52	0.42	.67	4.87
Visual memory	3	87	91	0.45	0.13 to 0.77	2.76	.006	2.24	0.98
Verbal memory	4	101	184	0.0	−0.51 to 0.51	0	.99	10.1*	0.75
Lifetime	3	78	67	0.18	−0.32 to 0.77	0.63	.53	4.78
Planning	4	81	122	0.47	0.05 to 0.90	2.20	.03	5.92	0.39
Lifetime	3	59	73	0.67	0.31 to 1.03	3.65	<.001	1.20
Working memory	4	94	213	0.13	−0.40 to 0.55	0.48	.63	11.58*	0.61
Lifetime	2	49	47	0.64	0.22 to 1.05	3.00	.003	0.16
Current/recent	2	45	166	−0.28	−0.61 to 0.06	1.62	.10	0.12

Note: Bold values indicate comparisons that were significantly different between the SCZ + CANN and the SCZ − CANN groups.

*P < .05.