Table 5.

Cognitive problems outside the laboratory

Age 38 y informant reports	Never used, never diagnosed, n = 228	Used, never diagnosed, n = 457	1 diagnosis, n = 71	2 diagnoses, n = 31	3+ diagnoses, n = 35	Linear trend t test*	P
Informant-reported attention problems†	−0.21	−0.07	0.31	0.64	0.96	7.74	<0.0001
Informant-reported memory problems†	−0.27	−0.03	0.38	0.78	0.75	7.65	<0.0001

Shown are informant reports of cognitive problems at age 38 y as a function of the number of study waves between ages 18 y and 38 y for which study members met criteria for cannabis dependence. Scores are standardized means adjusted for baseline (childhood) full-scale IQ assessed before the onset of cannabis use. These means can be interpreted as effect sizes, with values of 0.20, 0.50, and 0.80 reflecting small, medium, and large effects, respectively. Cognitive problems among persistent cannabis users were apparent to the “naked-eye.”

*To test for a dose–response effect, we conducted an ordinary least-squares regression, estimating the linear trend controlling for childhood full-scale IQ and sex.

^†Higher score indicates worse everday problems.