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Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study.

ABSTRACT: AIMS:This study tested whether adolescents who used cannabis or met criteria for cannabis dependence showed neuropsychological impairment prior to cannabis initiation and neuropsychological decline from before to after cannabis initiation. DESIGN:A longitudinal co-twin control study. SETTING AND PARTICIPANTS:Participants were 1989 twins from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative birth cohort of twins born in England and Wales from 1994 to 1995. MEASUREMENTS:Frequency of cannabis use and cannabis dependence were assessed at age 18. Intelligence quotient (IQ) was obtained at ages 5, 12 and 18. Executive functions were assessed at age 18. FINDINGS:Compared with adolescents who did not use cannabis, adolescents who used cannabis had lower IQ in childhood prior to cannabis initiation and lower IQ at age 18, but there was little evidence that cannabis use was associated with IQ decline from ages 12-18. For example, adolescents with cannabis dependence had age 12 and age 18 IQ scores that were 5.61 (t = -3.11, P = 0.002) and 7.34 IQ points (t = -5.27, P < 0.001) lower than adolescents without cannabis dependence, but adolescents with cannabis dependence did not show greater IQ decline from age 12-18 (t = -1.27, P = 0.20). Moreover, adolescents who used cannabis had poorer executive functions at age 18 than adolescents who did not use cannabis, but these associations were generally not apparent within twin pairs. For example, twins who used cannabis more frequently than their co-twin performed similarly to their co-twin on five of six executive function tests (Ps > 0.10). The one exception was that twins who used cannabis more frequently than their co-twin performed worse on one working memory test (Spatial Span reversed; ? = -0.07, P = 0.036). CONCLUSIONS:Short-term cannabis use in adolescence does not appear to cause IQ decline or impair executive functions, even when cannabis use reaches the level of dependence. Family background factors explain why adolescent cannabis users perform worse on IQ and executive function tests.

SUBMITTER: Meier MH

PROVIDER: S-EPMC5760333 | biostudies-other | 2018 Feb

REPOSITORIES: biostudies-other

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Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study.

Meier Madeline H MH Caspi Avshalom A Danese Andrea A Fisher Helen L HL Houts Renate R Arseneault Louise L Moffitt Terrie E TE

Addiction (Abingdon, England) 20170905 2

<h4>Aims</h4>This study tested whether adolescents who used cannabis or met criteria for cannabis dependence showed neuropsychological impairment prior to cannabis initiation and neuropsychological decline from before to after cannabis initiation.<h4>Design</h4>A longitudinal co-twin control study.<h4>Setting and participants</h4>Participants were 1989 twins from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative birth cohort of twins born in England and Wales f ...[more]

PMID: 28734078

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Project description:AimsTo estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments.DesignLongitudinal discordant twin and gene-environment interaction models in twins recruited from birth records and assessed prospectively.SettingThe United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized.ParticipantsTwo longitudinal, prospectively assessed samples of American twins aged 24-47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence.MeasurementsCurrent cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant's state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014.FindingsAccounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10-5 ). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2 = 2.9 × 10-9 , degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic = 0.24) compared with states that did not (rgenetic = 0.78, Pdifference = 0.016).ConclusionsIn the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

Dataset Information

Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study.

Publications

Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study.

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