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Associations between adolescent cannabis use and young-adult functioning in three longitudinal twin studies.

ABSTRACT: Observational studies have linked cannabis use to an array of negative outcomes, including psychiatric symptoms, cognitive impairment, and educational and occupational underachievement. These associations are particularly strong when cannabis use occurs in adolescence. Nevertheless, causality remains unclear. The purpose of the present study was thus to examine associations between prospectively assessed adolescent cannabis use and young-adult outcomes (psychiatric, cognitive, and socioeconomic) in three longitudinal studies of twins (n = 3,762). Twins reporting greater cumulative cannabis use in adolescence reported higher levels of psychopathology as well as poorer socioeconomic outcomes in young adulthood. However, cannabis use remained associated only with socioeconomic outcomes (i.e., educational attainment, occupational status, and income) in monozygotic-cotwin control analyses, which account fully for shared genetic and environmental confounding. Follow-up analyses examining associations between twin differences in adolescent cannabis use and longitudinal change in academic functioning during the middle- and high-school years provided a possible mechanism for these associations, indicating that greater cannabis use during this period was associated with decreases in grade point average and academic motivation as well as increases in academic problem behavior and school disciplinary problems. Our findings thus suggest that cannabis use in adolescence has potentially causal, deleterious effects on adolescent academic functioning and young-adult socioeconomic outcomes despite little evidence suggesting a strong, causal influence on adult mental health or cognitive ability.

SUBMITTER: Schaefer JD

PROVIDER: S-EPMC8040790 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description: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.

Project description:Background: Among youth already using cannabis, legalization of medical cannabis may influence cannabis-related attitudes and behaviors, including increasing access through use of someone else's medical cannabis (diversion). Objective: To examine cannabis-related attitudes and behaviors (including diverted cannabis use) in cannabis-using youth in the four years following medical cannabis legalization. Additionally, we investigated characteristics of youth who used vs. did not use diverted medical cannabis. Methods: Data were collected in Boston from 2013 (when medical cannabis legislation took effect in Massachusetts) through 2016 (when recreational cannabis use became legal in Massachusetts). Cannabis-using youth (age 13-24) presenting to an outpatient adolescent substance use treatment program (ASUTP) or recruited for an adolescent medicine clinic study (AMCS) completed a confidential survey on demographic characteristics and cannabis use behaviors and attitudes. We used multiple logistic regression to analyze changes in attitudes and behaviors over three years versus the reference year (2013), controlling for demographics. We used chi-square to compare characteristics of youth reporting use of diverted medical cannabis versus those not. Results: The sample included 273 cannabis-using youth (ASUTP n = 203, AMCS n = 70; 2013 n = 67, 2014 n = 67, 2015 n = 77, 2016 n = 62). Mean ± SD age was 18.2 ± 2.5 years, 32% were female, 58% were White non-Hispanic, and 70% had college-graduate parents. In 2013, most youth reported that cannabis was easy to obtain (97.9%), and that occasional cannabis use had "no" or "slight" risk of harm (89.4%), with little change across years. In 2016, 44% of youth reported using someone else's medical cannabis, versus 15% in 2013 (aOR 4.66, 95% CI 1.81, 11.95). Youth using diverted medical cannabis had higher likelihood of reporting riding with a driver, or driving themselves, after cannabis use (both p < .01). Conclusion: Among at-risk youth in Massachusetts, use of diverted medical cannabis increased after medical cannabis legalization, and those using diverted medical cannabis reported higher risk for cannabis-related traffic injury.

Project description:ObjectivesStudies examining the impact of adolescent and young adult cannabis use on structural outcomes have been heterogeneous. One already-identified moderator is sex, while a novel potential moderator is extent of aerobic fitness. Here, we sought to investigate the associations of cannabis use, sex, and aerobic fitness levels on brain volume. Second, we explored brain-behavior relationships to interpret these findings.MethodsSeventy-four adolescents and young adults (36 cannabis users and 38 controls) underwent 3 weeks of monitored cannabis abstinence, aerobic fitness testing, structural neuroimaging, and neuropsychological testing. Linear regressions examined cannabis use and its interaction with sex and aerobic fitness on whole-brain cortical volume and subcortical regions of interests.ResultsNo main-effect differences between cannabis users and nonusers were observed; however, cannabis-by-sex interactions identified differences in frontal, temporal, and paracentral volumes. Female cannabis users generally exhibited greater volume while male users exhibited less volume compared to same-sex controls. Positive associations between aerobic fitness and frontal, parietal, cerebellum, and caudate volumes were observed. Cannabis-by-fitness interaction was linked with left superior temporal volume. Preliminary brain-behavior correlations revealed that abnormal volumes were not advantageous in either male or female cannabis users.ConclusionsAerobic fitness was linked with greater brain volume and sex moderated the effect of cannabis use on volume; preliminary brain-behavior correlations revealed that differences in cannabis users were not linked with advantageous cognitive performance. Implications of sex-specific subtleties and mechanisms of aerobic fitness require large-scale investigation. Furthermore, present findings and prior literature on aerobic exercise warrant examinations of aerobic fitness interventions that aimed at improving neurocognitive health in substance-using youth.

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.

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Associations between adolescent cannabis use and young-adult functioning in three longitudinal twin studies.

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