Early-onset Cannabis Use Research Articles

Characteristics Associated With Cannabis Use Initiation by Late Childhood and Early Adolescence in the Adolescent Brain Cognitive Development (ABCD) Study

This cohort study evaluates characteristics associated with early-onset cannabis use.

Prospective Polysubstance use Profiles Among Adolescents with Early-onset Cannabis Use, and their Association with Cannabis Outcomes in Emerging Adulthood

Prospective Polysubstance use Profiles Among Adolescents with Early-onset Cannabis Use, and their Association with Cannabis Outcomes in Emerging Adulthood

Validating a brief screening measure for early-onset substance use during adolescence in a diverse, nationwide birth cohort

The Loeber Risk Score (LRS) was developed to predict early-onset cannabis use in adolescence from late childhood, facilitating early identification. However, the LRS was developed in non-representative historical samples, leaving uncertain its generalizability to children/adolescents across the U.S. today. We externally validated the LRS in a diverse, nationwide cohort (N = 4,898) weighted to the composition of the U.S. Census. Participants in 20 cities completed assessments when youth were approximately 5, 9, and 15 years old. Parents completed the LRS at the age ∼5 and ∼9 interviews. At the age ∼15 interview, youth reported on the onset of alcohol/drug use before age 15, monthly drinking/binge drinking at ages 14–16, and use of cannabis multiple times per month at ages 14–16. First, we validated the LRS measured at age ∼9. Area under the receiver operating curve was 0.62 for onset of cannabis use before age 15, 0.68 for onset of cigarette use before age 15, and 0.62 for use of cannabis multiple times per month at ages 14–16. For drinking outcomes, LRS performance could not be distinguished from chance prediction. The recommended screening cutoff of LRS ≥ 2 identified 24% of children, among whom early-onset cannabis/cigarette use outcomes occurred 1.4–2.2 times more frequently than the general population. The LRS’ performance did not vary significantly by sex, race, or ethnicity. When the LRS was measured at age ∼5, AUROC was significantly lower for some outcomes. Together, findings support the LRS measure as a potential tool for identifying children in early or late childhood at risk of early-onset drug use in adolescence.

Predictors of Early-Onset Cannabis Use in Adolescence and Risks for Substance Use Disorder Symptoms in Young Adulthood

Early detection of risks for substance use disorders is essential to lifelong health and well-being for some youth. Very early-onset use is proposed as an indicator of risk for substance use disorders, but risk and protective factors related to early-onset use have not been identified. The current study compared risk and protective factors that distinguish early- and late-onset cannabis users from abstainers using data collected from a large community sample. The study also examined onset-group differences in participants’ reports of substance use disorder symptoms a decade later. Heavy episodic drinking (early-onset: OR = 7.29 CI = [1.60, 33.19]) and engagement with peers involved in deviant behaviors (early-onset: OR = 2.50 CI = [1.50, 4.13]) are risk factors for early-onset cannabis use. Protective factors, including parent monitoring (early-onset: OR = 0.73 CI = [0.58, 0.93]), engagement with peers involved in positive behaviors (early-onset: OR = 0.54 CI = [0.39, 0.76]), school engagement (early-onset: OR = 0.83 CI = [0.72, 0.96]), and academic grades (early-onset: OR = 0.37 CI = [0.21, 0.65]) also predicted early versus later onset-group differences. Early age of onset may be distinctly related to risk and protective factors previously associated with risks for substance use in all adolescents.

Does Parents' Age at First Birth Moderate Intergenerational Continuity in Early-Onset Cannabis Use?

The aims of this brief report were to examine the extent to which early onset of cannabis use by parents and their children, and intergenerational continuity in early-onset cannabis use by parents and children, differ as a function of parent age at birth of first child. A total of 795 parent-child dyads (57% male parents and 49% male children) were compiled from three intergenerational studies: Oregon Youth Study-Three Generational Study (OYS-3GS), Rochester Youth Development Study and Rochester Intergenerational Study (RYDS-RIGS), and Seattle Social Development Project-The Intergenerational Project (SSDP-TIP). Parents and children identified as non-Hispanic White (29% and 22%, respectively), Black (55% and 47%), and Hispanic (8% and 11%). Early-onset cannabis use was defined as initiation at or before age 15. Time-varying effect models were fit to examine the research questions. Among parents, earlier initiation of cannabis use was associated with an earlier entry into parenthood. Moreover, parents' later age at first birth was predictive of a lower prevalence of early-onset cannabis use among their children. Last, regarding intergenerational continuity, parental early onset of cannabis use increased the likelihood of child early-onset use, but only among older parents (i.e., later age at first birth). We provide a nuanced examination of the associations between parental and child early-onset cannabis use as a function of parents' age at first birth and describe a novel approach to incorporating parent's age at first birth into models of intergenerational continuity.

Neurodevelopmental Effects of Cannabis Use in Adolescents and Emerging Adults with ADHD: A Systematic Review

Abstract Objective Systematically review the scientific literature to characterize the effects of cannabis use on brain structure, function, and neurodevelopmental outcomes in adolescents and young adults with ADHD. Method Systematic review following PRISMA guidelines utilizing PubMed, Embase, PsycINFO, and Cochrane CENTRAL trials register from inception until 1 January 2020. Articles that examined the impact of cannabis use on youth with ADHD were included. Results Eleven studies were identified that compared outcomes for individuals with ADHD who used cannabis or synthetic cannabinoids against those with ADHD who did not. Seven of these studies used neuroimaging techniques, including fMRI, structural MRI, and SPECT. Differential regions of activation were identified, including the right hippocampus and cerebellar vermis, and bilateral temporal lobes. Morphological differences were identified in the right precentral and postcentral gyri, left nucleus accumbens, right superior frontal and postcentral gyri. No study identified any additive or ADHD × cannabis use interaction on neuropsychological tasks of executive function. Two studies found adverse differential impacts of early-onset cannabis use in this population. Conclusion A dearth of evidence is available on the impact of cannabis use on the developing brain and functioning for individuals with ADHD, despite the elevated risk for substance use in this population. The limited, potentially underpowered evidence does not support the hypothesis that cannabis use has a deleterious impact on neuropsychological tasks in transitional age youth with ADHD. Larger and longer-term studies are needed, however, to better inform clinicians and patients as to the impacts of cannabis use in youth with ADHD.

Examining pathways between genetic liability for schizophrenia and patterns of tobacco and cannabis use in adolescence.

It is not clear to what extent associations between schizophrenia, cannabis use and cigarette use are due to a shared genetic etiology. We, therefore, examined whether schizophrenia genetic risk associates with longitudinal patterns of cigarette and cannabis use in adolescence and mediating pathways for any association to inform potential reduction strategies. Associations between schizophrenia polygenic scores and longitudinal latent classes of cigarette and cannabis use from ages 14 to 19 years were investigated in up to 3925 individuals in the Avon Longitudinal Study of Parents and Children. Mediation models were estimated to assess the potential mediating effects of a range of cognitive, emotional, and behavioral phenotypes. The schizophrenia polygenic score, based on single nucleotide polymorphisms meeting a training-set p threshold of 0.05, was associated with late-onset cannabis use (OR = 1.23; 95% CI = 1.08,1.41), but not with cigarette or early-onset cannabis use classes. This association was not mediated through lower IQ, victimization, emotional difficulties, antisocial behavior, impulsivity, or poorer social relationships during childhood. Sensitivity analyses adjusting for genetic liability to cannabis or cigarette use, using polygenic scores excluding the CHRNA5-A3-B4 gene cluster, or basing scores on a 0.5 training-set p threshold, provided results consistent with our main analyses. Our study provides evidence that genetic risk for schizophrenia is associated with patterns of cannabis use during adolescence. Investigation of pathways other than the cognitive, emotional, and behavioral phenotypes examined here is required to identify modifiable targets to reduce the public health burden of cannabis use in the population.

Early onset of cannabis use and violent behavior in psychosis

Although evidence from psychosis patients demonstrates the adverse effects of cannabis use (CU) at a young age and that the rate of CU is high in subgroups of young violent patients with psychotic disorders, little is known about the possible effect of the age of onset of CU on later violent behaviors (VB). So, we aimed to explore the impact of age at onset of CU on the risk of displaying VB in a cohort of early psychosis patients. Data were collected prospectively over a 36-month period in the context of an early psychosis cohort study. A total of 265 patients, aged 18-35years, were included in the study. Logistic regression was performed to assess the link between age of onset of substance use and VB. Among the 265 patients, 72 had displayed VB and 193 had not. While violent patients began using cannabis on average at age 15.29 (0.45), nonviolent patients had started on average at age 16.97 (0.35) (p=0.004). Early-onset CU (up to age 15) was a risk factor for VB (odds ratio=4.47, confidence interval [CI]: 1.13-20.06) when the model was adjusted for age group, other types of substance use, being a user or a nonuser and various violence risk factors and covariates. History of violence and early CU (until 15) were the two main risk factors for VB. Our results suggest that early-onset CU may play a role in the emergence of VB in early psychosis.

Age of onset of Cannabis use and cognitive function in first-episode non-affective psychosis patients: Outcome at three-year follow-up

BackgroundIn recent years, the effects of cannabis use on cognitive functions in patients with psychosis have been widely studied. Recently, special emphasis has been placed on the impact of age at the onset of consumption on cognition in these patients. Method349 patients with a first episode of non-affective psychosis were studied. Patients were classified as cannabis users and non-users. Users were divided, according to their age when they began using cannabis, into: early-onset (age < 16) and late-onset (age ≥ 16) users. Differences between groups at baseline were studied based on sociodemographic, clinical, and cognitive variables. The groups were longitudinally (3-year) compared on cognitive variables. ResultsOut of the 349 patients included in this study, 38.7% (N = 135) were cannabis users. Of them, 39.3% (N = 53) were early-onset and 60.7% (N = 82) were late-onset cannabis users. No baseline differences were found between the early-onset and late-onset groups on cognitive domains. Longitudinally, only patients who had withdrawn from cannabis use during follow-up showed a significant improvement in verbal memory. ConclusionOur results did not show differences between the early-onset group and the other two groups in long-term cognitive performance, even if they kept consuming cannabis during the first three years of disease progression. Further studies are needed to elucidate the true relationship between early-onset cannabis use and cognitive function in patients with a first episode of psychosis.

Developmental sensitivity to cannabis use patterns and risk for major depressive disorder in mid-life: findings from 40 years of follow-up.

Evidence regarding the association between cannabis use and depression remain conflicting, especially as studies have not typically adopted a longitudinal design with a follow-up period that was long enough to adequately cover the risk period for onset of depression. Males from the Cambridge Study in Delinquent Development (CSDD) (N = 285) were assessed seven times from age 8 to 48 years to prospectively investigate the association between cannabis use and risk of major depressive disorder (MDD). A combination of multiple analyses (logistic regression, Cox regression, fixed-effects analysis) was employed to explore the strength and direction of effect within different developmental stages. Multiple regression analyses revealed that early-onset cannabis use (before age 18) but not late-onset cannabis use (after age 27) was associated with a higher risk and shorter time until a subsequent MDD diagnosis. This effect was present in high-frequency [(odds ratio (OR) 8.83, 95% confidence interval (CI) 1.29-70.79]; [hazard ratio (HR) 8.69, 95% CI 2.07-36.52)] and low-frequency early-onset users (OR 2.41, 95% CI 1.22-4.76; HR 2.09, 95% CI 1.16-3.74). Effect of increased frequency of cannabis use on increased risk of subsequent MDD was observed only for use during adolescence (age 14-18) but not at later life stages, while controlling for observed and non-unobserved time-invariant factors. Conversely, MDD in adulthood (age 18-32) was linked to a reduction in subsequent cannabis use (age 32-48). The present findings provide evidence implicating frequent cannabis use during adolescence as a risk factor for later life depression. Future studies should further examine causality of effects in larger samples.

F129. COMBINED PATTERNS OF TOBACCO AND CANNABIS USE IN ADOLESCENCE AND THEIR ASSOCIATION WITH PSYCHOTIC EXPERIENCES: A LONGITUDINAL ANALYSIS

BackgroundThere has been increasing concern about potentially causal effects of tobacco use on psychosis, but epidemiological studies have been less robust in attempts to minimise effects of confounding than studies of cannabis use have been. We therefore aim to examine the association of patterns of cigarette and cannabis use with preceding and subsequent psychotic experiences, and compare patterns of confounding across these patterns.MethodsWe analysed repeated measures of cigarette and cannabis use during adolescence in a sample of 5,300 individuals in the Avon Longitudinal Study of Parents and Children birth cohort who had at least 3 measures of cigarette and cannabis use between ages 14–19 years. Cigarette and cannabis use data were summarised using longitudinal latent class analysis to identify longitudinal classes of substance use, and associations between classes and psychotic experiences at 18 years were assessed.ResultsPrior to adjusting for a range of potential confounders, there was strong evidence that early-onset cigarette-only use (4.3%), early-onset cannabis use (3.2%), and late-onset cannabis use (11.9%), but not later-onset cigarette-only use (14.8%) latent classes were associated with increased psychotic experiences compared to non-users (65.9%) (omnibus P<0.001). After adjusting for confounders, the association for early-onset cigarette-only use attenuated substantially (unadjusted odds ratio (OR) = 3.03, 95%CI 1.13, 8.14; adjusted OR = 1.78, 95%CI 0.54, 5.88), whereas those for early-onset (adjusted OR = 3.70, 95%CI 1.66, 8.25) and late-onset (adjusted OR = 2.97, 95%CI 1.63, 5.40) cannabis use were unchanged.DiscussionOur findings indicate that whilst individuals who use either cannabis or cigarettes during adolescence have an increased risk of developing subsequent psychotic experiences, the epidemiological evidence for this being causal is substantively more robust for cannabis than it is for tobacco

Visual attention to motion stimuli and its neural correlates in cannabis users.

Attention to motion stimuli and correct motion perception are vital for road safety. Although cannabis use has been associated with increased road crash risks, there is limited research on attentional processing of moving stimuli in cannabis users. This study investigated the neural correlates of the three-stimulus oddball task in cannabis users (n=18) and non-users (n=23) in response to moving stimuli. Stimulus contrast was under 16% against a low luminance background (M luminance<16cd/m2 ). The two groups did not differ in accuracy or in N2 peak amplitude; however, N2 latency was longer for target and standard stimuli in the cannabis group than in the control group. The cannabis group also showed a significantly reduced P3b amplitude in response to target stimuli. The AUDIT score was added as a random factor to the anova to rule out the effects of uneven alcohol consumption in the two groups. A significant group effect was found for N2 latency in response to target and standard stimuli and a significant interaction between the group, and the AUDIT score was found for the P3b peak amplitude for the distractor and standard stimuli, but not for the target stimuli. The results of this study suggest that cannabis use relates to reduced neural activity underlying attention to motion stimuli. Implications for regular early-onset cannabis use road safety are discussed.

Association of Combined Patterns of Tobacco and Cannabis Use in Adolescence With Psychotic Experiences

There is concern about potentially causal effects of tobacco use on psychosis, but epidemiological studies have been less robust in attempts to minimize effects of confounding than studies of cannabis use have been. To examine the association of patterns of cigarette and cannabis use with preceding and subsequent psychotic experiences, and to compare effects of confounding across these patterns. This cohort study used data from the Avon Longitudinal Study of Parents and Children, which initially consisted of 14 062 children. Data were collected periodically from September 6, 1990, with collection ongoing, and analyzed from August 8, 2016, through June 14, 2017. Cigarette and cannabis use data were summarized using longitudinal latent class analysis to identify longitudinal classes of substance use. Associations between classes and psychotic experiences at age 18 years were assessed. Depending on the analysis model, exposures were longitudinal classes of substance use or psychotic experiences at age 12 years. Logistic regression was used to examine the associations between substance use longitudinal classes and subsequent onset of psychotic experiences. Longitudinal classes were derived using 5300 participants (56.1% female) who had at least 3 measures of cigarette and cannabis use from ages 14 to 19 years. Prior to adjusting for a range of potential confounders, there was strong evdience that early-onset cigarette-only use (4.3%), early-onset cannabis use (3.2%), and late-onset cannabis use (11.9%) (but not later-onset cigarette-only use [14.8%]) latent classes were associated with increased psychotic experiences compared with nonusers (65.9%) (omnibus P < .001). After adjusting for confounders, the association for early-onset cigarette-only use attenuated substantially (unadjusted odds ratio [OR], 3.03; 95% CI, 1.13-8.14; adjusted OR, 1.78; 95% CI, 0.54-5.88), whereas those for early-onset cannabis use (adjusted OR, 3.70; 95% CI, 1.66-8.25) and late-onset cannabis use (adjusted OR, 2.97; 95% CI, 1.63-5.40) remained consistent. In this study, our findings indicate that while individuals who use cannabis or cigarettes during adolescence have an increased risk of subsequent psychotic experiences, epidemiological evidence is substantively more robust for cannabis use than it is for tobacco use.

Persistent and Long-Term Neuropsychiatric Implications of Cannabis Use in Adolescents

Persistent and Long-Term Neuropsychiatric Implications of Cannabis Use in Adolescents

Child maltreatment and cannabis use in young adulthood: a birth cohort study.

To investigate whether: (1) child maltreatment is associated with life-time cannabis use, early-onset cannabis use, daily cannabis use and DSM-IV cannabis abuse in young adulthood; and (2) behaviour problems, tobacco use and alcohol use at age 14 are associated with cannabis use. Birth cohort using linked government agency child protection data to define exposure to child maltreatment. The Mater-University of Queensland Study of Pregnancy in Brisbane, Australia. Of the original cohort of 7223 mother and child pairs, obtained from consecutive presentations for prenatal care at a hospital serving a cross-section of the community, 3778 (52.3%) of the young people participated at age 21years. Exposure to child maltreatment was established by substantiated government agency reports. Cannabis outcomes were by self-report questionnaire and Composite International Diagnostic Interview (CIDI)-Auto at age 21. Associations were adjusted for a range of potential confounders. Additional adjustment was carried out for variables measured at age 14-youth behaviour problems [Achenbach Child Behavior Checklist (CBCL)], tobacco use and alcohol use. After adjustment, substantiated child maltreatment was associated with any life-time cannabis use [odds ratio (OR)=1.60, 95% confidence interval (CI)=1.08-2.39], cannabis use prior to age 17 (OR=2.47, 95% CI=1.67-3.65), daily cannabis use (OR=2.68, 95% CI=1.49-4.81) and DSM-IV cannabis abuse/dependence (OR=1.72, 95% CI=1.07-2.77). Externalizing behaviour and tobacco and alcohol use at age 14 were associated significantly with almost all cannabis outcomes (P<0.05), with internalizing behaviour associated inversely (P<0.05). Children in Australia who are documented as having been maltreated are more likely to go on to use cannabis before the age of 17, use cannabis as an adult, use cannabis daily and meet DSM-IV criteria for cannabis dependence. Externalizing behaviour in adolescence appears partly to mediate the association with adult cannabis use.

Intergenerational Continuity in Cannabis Use: The Role of Parent's Early Onset and Lifetime Disorder on Child's Early Onset

PurposeChildren's early onset of cannabis use was examined as a function of their parent's early onset of cannabis and subsequent incidence of a lifetime cannabis abuse or dependence disorder. MethodsProspective, longitudinal data from the Rochester Youth Development Study and the Rochester Intergenerational Study for 442 parent-child dyads (274 father-child, 168 mother-child) were used. The children were evenly split by sex. Logistic regression models and a path analysis were estimated to assess the effect of parent's cannabis use on child's onset of cannabis by age 15. ResultsFathers who began using cannabis by age 15 were more likely to meet the criteria for a lifetime cannabis disorder (odds ratio = 5.66, 95% confidence interval = 1.89–16.90). The offspring of fathers who met the criteria for a disorder had higher odds of early initiation of cannabis use (odds ratio = 9.70, 95% confidence interval = 3.00–31.34). Early-onset cannabis use by father was indirectly associated with their child's onset of cannabis use via father's lifetime cannabis disorder. No significant effects for mothers were observed, although analyses were limited due to the low rate of mothers who met the criteria for a lifetime cannabis disorder. ConclusionsThis study provides evidence of intergenerational continuity in cannabis use among fathers and their children and confirms the need to consider timing of use and intervening mechanisms in the study of continuity in cannabis use across generations.

Long-term cannabis abuse and early-onset cannabis use increase the severity of cocaine withdrawal during detoxification and rehospitalization rates due to cocaine dependence

BackgroundLong-term and early-onset cannabis consumption are implicated in subsequent substance- related problems. The aim of this follow-up study was to investigate whether these patterns of cannabis use could impact cocaine withdrawal severity and cocaine craving intensity during detoxification. In addition, we investigated their impact in the rehospitalization rates due to cocaine dependence 2.5 years after detoxification assessment. MethodsThe sample was composed of 93 female cocaine-dependent inpatients who were enrolled in an inpatient detoxification unit. Cocaine withdrawal symptoms were measured at the 4th, 9th and 14th days of detoxification using the cocaine selective severity assessment (CSSA). Data on the age of first years of drug use – alcohol, cannabis and cocaine – and the years of substance abuse were obtained using the Addiction Severity Index (ASI-6). Other relevant clinical variables were also investigated, including a 2.5 years follow-up assessment of number of rehospitalization due to cocaine dependence. ResultsEarly-onset cannabis use and long-term cannabis abuse were associated with an increase instead of a reduction in the severity of cocaine withdrawal symptoms and craving intensity during detoxification. In addition, long-term cannabis abuse predicted higher number of rehospitalization due to cocaine dependence after 2.5 years of the first detoxification assessment. ConclusionsEarly-onset cannabis use and long-term cannabis abuse are associated with a worse detoxification treatment response. Our findings may help to identify patients who will struggle more severely to control cocaine withdrawal syndrome during early drug abstinence, and indicate that cannabis use prior to cocaine withdrawal should be considered an adverse factor.

A randomized controlled trial of a brief motivational enhancement for non-treatment-seeking adolescent cannabis users

Evidence for negative effects of early-onset cannabis use has led to a need for effective interventions targeting adolescent cannabis users. A randomized controlled trial of an Australian two-session intervention based on motivational interviewing (the ACCU, or Weed-Check in Dutch) was replicated in a larger Dutch sample of 119 non-treatment-seeking adolescent cannabis users. Outcome measures at the 3-month follow-up were quantity and frequency of cannabis use, symptoms of dependence, stage of change, and psychosocial functioning. Changes in all measures were in the expected direction, yet not significant. In moderation analyses, heavier cannabis users at baseline receiving the Weed-Check had greater reductions in cannabis use than those in the control condition. These results suggest that the Weed-Check might be beneficial for heavier cannabis-using adolescents. Further research is needed to confirm these results in a sample of adolescent heavy cannabis users and to examine the relationship between MI skills of prevention workers and outcome.

Cannabis controversies: how genetics can inform the study of comorbidity.

To review three key and controversial comorbidities of cannabis use-other illicit drug use, psychosis and depression, as well as suicide, from a genetically informed perspective. Selective review. Genetic factors play a critical role in the association between cannabis use, particularly early-onset use and use of other illicit drugs, psychosis and depression, as well as suicide, albeit via differing mechanisms. For other illicit drugs, while there is strong evidence for shared genetic influences, residual association that is attributable to causal or person-specific environmental factors cannot be ruled out. For depression, common genetic influences are solely responsible for the association with cannabis use but for suicidal attempt, evidence for person-specific factors persists. Finally, even though rates of cannabis use are inordinately high in those with psychotic disorders, there is no evidence of shared genetic etiologies underlying this comorbidity. Instead, there is limited evidence that adolescent cannabis use might moderate the extent to which diathesis influences psychosis. Overlapping genetic influences underlie the association between early-onset cannabis use and other illicit drug use as well as depression and suicide. For psychosis, mechanisms other than shared genetic influences might be at play.

Is the relationship between early-onset cannabis use and educational attainment causal or due to common liability?

BackgroundSeveral studies have shown that early cannabis use is correlated with poor educational performance including high school drop-out. The predominant explanation for this relationship is that cannabis use causes disengagement from education. Another explanation is that the association between early cannabis use and educational attainment is not causal, but the result of overlapping risk factors that increase the likelihood of both early cannabis use and disengagement from education. These confounding factors could be of genetic and/or environmental origin. MethodsHere we use data from a large community-based sample of adult twins (N=3337) who completed a comprehensive semi-structured telephone interview. We first apply the classical twin-design to determine whether genetic and/or environmental influences underlie the relationship between early-onset cannabis use (prior to age 18) and early school leaving. Next, with a co-twin control design we investigate whether the relationship between the two variables is more likely due to direct causality or overlapping risk factors. ResultsWe find a significant phenotypic correlation between early-onset cannabis use and early school leaving (r=0.26), which could be explained by familial influences (of genetic and/or shared environmental origin). The pattern of odds ratios found in the co-twin control design is not consistent with direct causation, but rather suggests that the association is due to shared environmental factors influencing both variables. ConclusionOur findings suggest that the relationship between early-onset cannabis use and school leaving is due to shared environmental risk factors influencing both the risk of early-onset cannabis use and early school leaving.