Table 4.

Change in cognitive function (from 13–14 to 20 years) and cannabis use age of onset, frequency at 14 years (intercept), and growth from 14 to 17 years

	Vocabularya		Number Randomization		DS Forward		DS Backward		SOP		PAL		Conditional Association		CAPT
	β	p	β	p	β	p	β	p	β	p	β	p	β	p	β	p
Model 1
Age of onset	0.11	.034	−0.02	.78	−0.05	.43	0.01	.92	0.12	.04	0.07	.21	0.17	.010	−0.01	.93
Verbal IQ at 13	0.26	<.001	−0.15	.025	−0.12	.09	−0.15	.014	0.21	<.001	−0.07	.34	0.02	.76	−0.05	.49
Age at adult testing	0.06	.20	0.12	.041	0.05	.41	0.01	.85	−0.10	.056	0.03	.52	0.14	.012	−0.24	<.001
Family risk	−0.35	<.001	−0.02	.73	0.03	.60	−0.05	.43	−0.11	.052	0.04	.56	0.22	<.001	0.04	.55
Cannabis use 20	−0.01	.90	−0.03	.72	−0.39	<.001	−0.05	.52	−0.22	.001	0.08	.18	0.09	.24	0.00	.97
Tobacco use 20	−0.10	.08	0.00	.97	0.15	.010	−0.01	.87	0.04	.43	−0.03	.61	0.04	.51	0.15	.023
Other drug use 20	0.19	.001	0.00	.97	0.29	<.001	0.02	.79	0.17	.006	0.02	.65	−0.05	.52	−0.13	.08
PAL 14	0.03	.70	0.14	.033	0.09	.28	0.28	<.001	0.19	.007	−0.54	<.001	0.23	.010	−0.05	.61
SOP 14	0.16	.002	0.12	.063	0.20	.001	−0.01	.95	−0.47	<.001	0.00	.99	−0.17	.012	−0.17	.025
Academic achieve 13–15	−0.02	.76	−0.04	.61	−0.05	.43	0.13	.10	0.00	.99	−0.01	.93	0.00	.99	0.00	.97
R2	0.35	<.001	0.04	.08	0.12	.001	0.11	.001	0.39	<.001	0.37	<.001	0.12	.001	0.12	.004
Model 2
Cannabis intercept	0.02	.82	0.16	.19	0.20	.064	0.04	.70	0.01	.92	−0.02	.81	−0.15	.10	−0.29	.002
Cannabis slope	−0.17	.042	−0.19	.09	−0.02	.84	−0.02	.78	−0.12	.16	0.02	.86	−0.28	.004	0.08	.47
R2	0.36	<.001	0.08	.06	0.14	<.001	0.11	<.001	0.39	<.001	0.37	<.001	0.18	<.001	0.18	<.001
Model 3
Cannabis intercept	0.01	.85	0.16	.18	0.19	.07	0.03	.71	−0.01	.94	−0.02	.80	−0.15	.18	−0.28	.002
Cannabis slope	−0.17	.016	−0.19	.09	−0.02	.83	−0.03	.77	−0.12	.15	0.01	.88	−0.28	.003	0.08	.45
Age onset (residual)	0.04	.39	−0.03	.67	0.06	.36	0.00	.99	0.04	.52	0.05	.22	−0.06	.33	−0.12	.062
R2	0.36	<.001	0.08	.06	0.15	<.001	0.12	.001	0.40	<.001	0.37	<.001	0.18	<.001	0.19	<.001
Model 4
Cannabis intercept	0.05	.51	0.23	.20	0.21	.17	0.08	.57	0.14	.31	−0.02	.87	−0.07	.65	−0.37	.003
Cannabis slope	−0.11	.16	−0.19	.12	−0.01	.91	−0.01	.94	−0.07	.43	0.05	.52	−0.21	.028	0.04	.74
Age onset (residual)	0.02	.77	−0.05	.44	0.05	.43	−0.01	.93	0.00	.98	0.04	.36	−0.08	.15	−0.11	.11
High-school graduation	0.21	<.001	0.08	.36	−0.06	.43	−0.03	.69	0.07	.33	0.11	.08	0.02	.76	0.05	.53
ADHD 13–15 years	−0.11	.07	0.18	.043	0.07	.38	−0.09	.27	−0.04	.57	0.08	.26	0.10	.19	−0.02	.82
CD 13–15 years	−0.09	.12	−0.05	.49	0.11	.21	0.03	.63	−0.11	.18	−0.10	.17	−0.05	.49	0.09	.23
Alcohol use 13–17 years	−0.03	.67	0.05	.41	0.01	.89	0.04	.62	−0.02	.71	−0.17	.024	−0.16	.025	0.04	.63
Tobacco use 13–17 years	0.01	.90	−0.20	.17	−0.15	.24	−0.11	.32	−0.13	.23	0.16	.13	−0.07	.59	0.10	.52
R2	0.41	<.001	0.11	.033	0.17	<.001	0.12	.001	0.42	<.001	0.40	<.001	0.20	<.001	0.20	<.001

Note: The sign for the variables that code for errors was changed so that higher scores on any measure indicates better ability. The results using change scores are presented, but analyses using neurocognitive residualized scores and baseline scores as covariates were also conducted, with equivalent results. Values in bold indicate that they remain significant after controlling for multiple testing. DS, Digit span; SOP, self-ordered pointing; PAL, paired associates learning; CAPT, Card Playing Task. Model fit for Model 1: χ² (2) = 1.83, root mean square error of approximation (RMSEA) = 0.00, comparative fit index (CFI) = 1.00, standardized root mean square residual (SRMR) = 0.01; Model 2: χ² (39) = 94.46, RMSEA = 0.07, CFI = 0.95, SRMR = 0.03; Model 3: χ² (41) = 101.28, RMSEA = 0.07, CFI = 0.95, SRMR = 0.03; Model fit for Model 4: χ² (51) = 101.43, RMSEA =0.06, CFI =0.96, SRMR =0.02. Although only presented under Model 1, standardized coefficients are adjusted for age at testing in adulthood; family risk; average academic achievement 13–15; verbal IQ at 13; SOP and PAL at 14; and concurrent cannabis, alcohol, stimulant, and tobacco use frequency at 20 years in all models.

^aThe verbal IQ change score was calculated by standardizing the sentence completion task (verbal IQ) at 13 years (z scores) and subtracting it from standardized (z-scored) vocabulary scores at 20 years. Analyses using change scores computed using the vocabulary subtest at 15 years as baseline scores were equivalent to those reported here (differing only by a few decimals), with analyses yielding equivalent results (see Data Preparation and Statistical Analysis section in the online supplementary material).