Table 1.

Characteristics of Longitudinal Studies on Cannabis Use and Changes in Neuropsychological Functioning.

Study	Sample Characteristics	Sampling Method	Time Points Considered	Criteria for Classification	CU Groups	CU Amount/Frequency	Other SU Data Collected	Other SU Amount/Frequency	NP Domains Assessed	NP Domains Associated with CU
Fried et al. (2005)	N=113; primarily White; 55.8% male; $\overline{x}$ age at follow-up = 18	Random selection	2 assessments (ages 9-12 and 17-21)	Current CU status and frequency	Controls; Former regular users; Current light users; Current heavy users	Current CU ($\overline{x}$ joints/wk)/Cumulative CU ($\overline{x}$ joints total): Current light users: 1.4/122; Current heavy users: 12.4/1884; Former regular users: 0/2203	Current alcohol use ($\overline{x}$ drinks during wk before testing), current tobacco use ($\overline{x}$ cigarettes per day)	$\overline{x}$ drinks wk before test: Controls: .3; Current light users: 2.5; Current heavy users: 2.1; Former users: 3.1. $\overline{x}$ cigarettes per day: Controls: .2; Current light users: 2.2, Current heavy users: 9.6; Former users: 6.2	IQ, Vocabulary, Memory (immediate and delayed recall, working memory), sustained attention, abstract reasoning	Overall IQ, processing speed, immediate and delayed recall
Meier et al. (2012)	N=1,037; primarily White; 52% male; $\overline{x}$ age at last follow-up = 38	Rep. birth cohort	CU: 5 assessments(ages 18, 21, 26, 32, 38) NP: 2 assessments (ages 13 and 38)	A) Total assessments participant met criteria for cannabis dependence B) Total assessments when participant CU 4+ days/wk	A) No CU; Used but never diagnosed; Diagnosed at 1 wave; Diagnosed at 2 waves; Diagnosed at 3 or more waves B) No CU; Used but never regularly; Regular CU at 1 wave; Regular CU at 2 waves; Regular CU at 3 waves	Median days of past year use among persistent users: infrequent adolescent-onset CU = 14; frequent adolescent-onset CU = 365; infrequent adult-onset CU = 6; frequent adult-onset CU = 365.	Number of assessments when participants met criteria for tobacco, alcohol, and other drug dependence	N/A	IQ, memory, executive functioning, processing speed, perceptual reasoning, verbal comprehension	IQ, memory, executive functioning, processing speed, perceptual reasoning, verbal comprehension
Tait et al. (2011)	N=2,404; race = N/A; 45% male; $\overline{x}$ age at baseline = 23	Rep. sample with random selection	3 assessments (baseline, 2 follow-ups at 4 year intervals)	Current CU status and frequency	Never used; Always former; Former light; Former heavy; Remain light; Remain heavy	N/A	N/A	N/A	Memory (immediate and delayed recall, episodic memory, working memory), verbal ability, attention and motor speed	Immediate Recall
McKetin et al. (2016)	N=1,897; primarily White; 42.5% male; $\overline{x}$ age at baseline = 43	Rep. sample with random selection	3 assessments (baseline and 3 follow-ups at 4 year intervals)	Past year CU frequency	No use in past year; < wkly past year use; ≥ wkly past year use	N/A	Tobacco use (never/past/current), alcohol consumption (AUDIT score, levels based on heaviest past drinking frequency and amount)	No past year CU group mean AUDIT score = 4.2; Less than wkly CU group mean AUDIT score = 7.1; Wkly or greater CU group mean AUDIT score = 6.6	Memory (immediate and delayed recall, working memory), premorbid verbal ability, attention and motor speed	Immediate recall, but no within subject effects
Jacobus et al. (2015)	N = 108; 62.6% white; 65.3% male; $\overline{x}$ age at baseline = 18	Community Sample	3 assessments (baseline, 2 follow-ups at 1.5 year intervals)	A) Lifetime CU and alcohol use frequency; B) Age of onset of CU	A) Marijuana users with concomitant alcohol use; Controls B) Early onset of regular CU; Late onset of regular CU; Controls	$\overline{x}$ lifetime CU episodes: Users: 1086.4 Controls: 87.2; $\overline{x}$ CU episodes from Baseline to Year 3: Users: 292.4 Controls: 26.0; $\overline{x}$ days of past month CU at baseline: Users: 15.5 Controls: 0.1. $\overline{x}$ days of past month CU at Year 3: Users: 13.3 Controls: 3.7	Current alcohol use (drinks per month), lifetime number of alcohol use episodes, lifetime other drug use episodes, average number of cigarettes per day in past wk	Drinks per month at baseline: Users: 47.8, Controls: 5.1; Drinks per month at Year 3L Users: 51.2, Controls: 32.3; Lifetime number of alcohol use episodes: Users: 644.9, Controls: 180.2; Lifetime other drug use episodes: Users: 84.4, Controls: 7.5; $\overline{x}$ cigarettes per day at baseline: Users: 0.8, Controls: 0.1; Average cigarettes per day at Year 3: Users: 0.8, Controls: 0.3	Complex attention, memory (working memory, verbal memory), processing speed, executive functioning, visuospatial functioning	Complex attention, memory, processing speed, visuospatial functioning
Mokrysz, et al. (2016)	N=2,235; primarily White; 46.6% male; $\overline{x}$ age at baseline = 8	Rep. birth cohort	CU: 1 assessment (age 15) NP: 4 assessment (ages 8, 11, 15, 16)	Lifetime CU frequency	No CU; CU < 5 times; CU 5-19 times; CU 20-49 times; CU ≥ 50 times	% reported typically smoking 1/16th ounce in less than 1 day: CU < 5 times: 14.3%; CU 5-19 times: 18.1%; CU 20-49 times: 30.2%; CU ≥ 50 times: 38.9%	Cumulative tobacco and alcohol consumption (number of times), number of other recreational drugs used	CU > 50: 97.3% used alcohol >20 times, 83.8% used tobacco > 20 times, 67.3% used other drugs. CU 20-49: 71.8% used alcohol and tobacco >20 times, 54.9% used other drugs. CU 5-19: 77.4% used alcohol >20 times, 52.6% used tobacco >20 times, 43.6% used other drugs. CU < 5: 63.7% used alcohol >20 times, 34.3% used tobacco >20 times, 28.6% used other drugs. No CU: 26.4% used alcohol >20 times, 4.5% used tobacco >20 times, 5.7% used other drugs	IQ, educational outcomes	None
Jackson et al. (2016)	RFAB: N = 789; 37% Hispanic, 27% White, 14% Black, 5% Asian, 17% Mixed; 48% male; 46% monozygotic; $\overline{x}$ age at baseline = 10 MTFS: N = 2,277; 93% White; 49% male; 63% monozygotic $\overline{x}$ age at baseline = 12	Comm. & population based sample	5 assessment points over 10 years (ages 9-10, 11-13, 14-15, 16-18, 19-20)	A) CU initiation B) CU frequency	A) Users; Nonusers B) CU more than 30 times; Daily CU for at least 6 months	N/A	Maximal binge drinking (number of drinks), cumulative other drug use (dichotomous)	$\overline{x}$ maximal binge-drinking: 2.7 for nonusers, 7.6 for users. Other drug use: 1.6% of nonusers, 38.3% of users	IQ	IQ (verbal ability and general knowledge)

^*Notes. Comm. Sample = Community Sample; Rep. = Representative; CU = Cannabis use; NP = Neuropsychological.