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Associations of Adolescent Cannabis Use with Academic Performance and Mental Health: A Longitudinal Study of Upper Middle Class Youth*

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Background: There is a hypothesis that low socioeconomic status (SES) may explain the link between cannabis use and poorer academic performance and mental health. A key question, therefore, is whether adolescent cannabis use is associated with poorer academic performance and mental health in high SES communities where there is reduced potential for confounding. Methods: Youth (n=254) from an upper middle class community were followed prospectively through the four years of high school (from age 14/15 to age 17/18). Past-year frequency of cannabis use was assessed annually. Official school records of academic performance and self-reported mental health symptoms (externalizing and internalizing symptoms) were assessed in grades 9 and 12. Results: Persistent cannabis use across the four years of high school was associated with lower grade-point average (β=-0.18, p=.006), lower Scholastic Aptitude Test (SAT) score (β=-0.13, p=.038), and greater externalizing symptoms (β=0.29, p<.001) in 12th grade, but not with greater internalizing symptoms (β=0.04, p=.53). Moreover, persistent cannabis use was associated with lower grade-point average (β=-0.13, p=.014) and greater externalizing symptoms (β=0.24, p=.002) in 12th grade, even after controlling for 9th grade levels of these outcomes. Similar associations were observed for persistent alcohol and tobacco use. Effects for persistent cannabis use became non-significant after controlling for persistent alcohol and tobacco use, reflecting the difficulties of disentangling effects of cannabis from effects of alcohol and tobacco. Conclusions: Low SES cannot fully explain associations between cannabis use and poorer academic performance and mental health.
... Adolescence is also a "perfect storm" for sleep problems (Carskadon, 2011), with 69% of U.S. high school students reporting insufficient sleep duration (≤7 h; Wheaton, Olsen, Miller, & Croft, 2016) and 10-12% reporting clinically-significant insomnia symptoms (grades 7-11; Alvaro, Roberts, Harris, & Bruni, 2017). Biopsychosocial consequences have been documented for both adolescent cannabis use (e.g., academic performance, externalizing problems, and long-term substance disorder risk; Levine, Clemenza, Rynn, & Lieberman, 2017;Meier, Hill, Small, & Luthar, 2015) and sleep problems (e.g., academic performance, depression/anxiety symptoms, motor vehicle accidents, and long-term cardiovascular risk; Donskoy & Loghmanee, 2018). ...
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Introduction Adolescents are at risk for both sleep problems and cannabis use. Despite emerging evidence for college students’ self-medication with cannabis to help sleep, generalizability to earlier developmental stages remains unknown. This study remedied this literature gap by characterizing high school students’ cannabis sleep aid use in terms of psychosocial correlates and prospective associations with substance use and sleep. Methods Data were drawn from a longitudinal urban adolescent health behavior study, Project Teen, including 407 9th-11th graders (Year 1 Mage=16.00 [SD=1.08, range=13-19]; 58% female; 41% Black, 22% White, 18% Asian, 17% multiracial, 2% Native Hawaiian or other Pacific Islander, 1% American Indian or Alaska Native; 12% Hispanic/Latinx). Students completed two web-based surveys (Minterval=388.89 days [SD=27.34]) assessing substance use and sleep at Year 1 (Y1) and Year 2 (Y2). Results Students reporting lifetime cannabis sleep aid use (8%) endorsed greater depression and anxiety symptoms at Y1, as well as greater cannabis, alcohol, and cigarette use (but not insomnia symptoms or sleep durations) at Y1 and Y2, compared to non-using peers. Over one year, cannabis sleep aid use was associated with increased cannabis dependence symptoms among students using cannabis, past-2-week binge drinking among students using alcohol, and lifetime cigarette use. However, cannabis sleep aid use was not prospectively associated with changes in insomnia symptoms or sleep durations. Conclusions Although replication is needed, cannabis sleep aid use among high school students may be associated with exacerbated cannabis dependence symptoms and increased binge drinking and cigarette use over time, without the intended sleep benefit.
... The following protective factors were also considered: physical activity, playing on a sports team, and academic performance. Other studies have noted the protective effect of these factors on mental health outcomes (Babiss & Gangwisch, 2009;Esch et al., 2014;Felez-Nobrega et al., 2020;McDowell et al., 2017;McMahon et al., 2017;McPhie & Rawana, 2015;Meier et al., 2015;Rao, 2018;Taliaferro et al., 2008). The specific survey questions and coding used for these risk and protective factors are presented in Table 1. ...
Article
This study examined the association between self-reported sports- or physical activity-related concussion (SPAC) and symptoms of depression and suicidal behaviors (suicidal ideation, having a suicide plan, and suicide attempts). This study used data from the 2017 and 2019 Youth Risk Behavior Survey (YRBS), a biennial, school-based, nationally representative survey of U.S. students in grade levels 9 to 12 (N = 14,496). Multivariate logistical regression models assessed the relationship between self-reported sports-or physical activity-related concussions and suicidal behaviors among students, controlling for a range of demographic and psychosocial variables. Altogether, 13.6% of students reported a sports-or physical activity related concussion in the past 12 months. Among youth, sports-or physical activity related concussions were significantly associated with greater odds of symptoms of depression, suicidal ideation, making a suicide plan, and suicide attempts compared to other youth who did not experience SPAC. Findings highlight increased risk for adverse mental health outcomes among students with sports-or physical activity related concussions. Providing resources for students to engage in physical activity and sports teams may help prevent the onset of depression and suicidal behaviors; however, resources must also be available to monitor any concussions related to these activities to provide support for student emotional well-being.
... The disruption of the dynamic between the upper brain and lower brain is also evident in other pathological behaviors including, but not limited to, substance abuse (Koob and Le Moal, 2001;Koob and Volkow, 2009;Koob and Schulkin, 2019), pornography consumption (Beauregard et al., 2001;Kuhn and Gallinat, 2014;Camilleri et al., 2020), etc. iv. Cannabis, hypnosis and COVID-19: Despite the political and other support evident in relation to cannabis, cannabis is no different from other drugs of abuse in its association with psychopathology (Nunez and Gurpegui, 2002;Lupica et al., 2004;Pistis et al., 2004;Fattore et al., 2010;Murray et al., 2014;Renard et al., 2014;Ballinger et al., 2015;Meier et al., 2015). Moreover, cannabis is known for its hypnotic effects (Monti, 1977;Kesner and Lovinger, 2020). ...
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As a behavioral neuroscientist focused on psychopathology, the happenings pertaining to the measures taken to address COVID-19 and their consequences are as much of interest as anything other work that I do. This document is a collation of quotes and some comments pertaining to every aspect of COVID-19 and its impact on the brain and behavior, on the individual and on society as a whole. The same document is updated weekly (generally) and also available on the web at: https://sammutlab.com/covid-19-resources/
... Cannabis use and sales may have considerable social and public health consequences. A monthly use has been associated with increased risk of psychosis, injuries, and poor obstetric outcomes when compared with non-user populations [3][4][5][6], as well as poor academic performance and decreased motivation [6][7][8]. Additionally, it has been recommended by the World Health Organization that cannabis is rescheduled in the international drug control framework from Schedule IV (particularly harmful and with few therapeutic properties) to Schedule I (especially serous risk to public health and limited if any therapeutic usefulness) [9]. While cannabis' health effects remain disputed, cannabis has been found addictive and may be associated with the risk of other substance use disorders according to a study drawing from national surveys by the US "National Institute on Alcoholism and Alcohol Abuse" [10]. ...
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Background Cannabis policy varies greatly across European countries, but evidence of how such policy impacts on recreational cannabis use among young people is conflicting. This study aimed to clarify this association by investigating how changes in cannabis legislation influenced cannabis use. Methods Available data on self-reports of recreational cannabis use among individuals aged 15–34 years was retrieved from EMCDDA. Information on cannabis policy changes was categorized as more lenient (decriminalisation or depenalisation) or stricter (criminalisation, penalisation). Countries that had implemented changes in cannabis legislation or had information on prevalence of use for at least eight calendar years, were eligible for inclusion. We used interrupted time-series linear models to investigate changes in country-specific trajectories of prevalence over calendar time and in relation to policy changes. Results Data from Belgium, Czech Republic, Germany, Italy, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden and United Kingdom, for 1994–2017 was available for analyses. Cannabis use varied considerably over the study period and between countries. On average, use was stable or weakly increasing in countries where legislation was not changed or changed at the extremes of the study period (+0.08 percent per year [95% CI -0.01, 0.17 percent]). In contrast, the pooled average use decreased after changes in legislation, regardless of whether it had become more lenient (-0.22 [-1.21, 0.77]) or stricter (-0.44 [-0.91, 0.03]). Conclusions Our findings do not support any considerable impact of cannabis legislation on the prevalence of recreational cannabis use among youth and young adults in Europe.
... Although effective treatments for adolescent SUDs are available, less than 10% of adolescents in need of substance use treatment receive it (SAMHSA, 2020). Untreated SUDs during adolescence are associated with poor mental health (Brook et al., 2016), poor academic performance (Meier et al., 2015), increased risk of death by suicide (Fontanella et al., 2020), and increased risk of having an SUD in adulthood (D'Amico et al., 2005). Frequently cited barriers to treatment include stigma toward substance use treatment services, low perceived need for treatment, not feeling ready for treatment, and confidentiality concerns (Berridge et al., 2018;Mensinger et al., 2006). ...
Article
Objective Screening, brief intervention, and referral to treatment (SBIRT) is a systematic approach to identification and intervention for individuals at risk for substance use disorders. Prior research indicates that SBIRT is underutilized in pediatric primary care. Yet few studies have examined procedures for identifying and addressing substance use in clinics that serve publicly insured adolescents (i.e., federally qualified health centers [FQHC]). This descriptive, multi-method study assessed adolescent substance use frequency and provider perspectives to inform SBIRT implementation in an urban pediatric FQHC in California. Methods A medical record review assessed substance use frequency and correlates among publicly insured adolescents aged 12–17 years who completed a well-child visit in pediatric primary care between 2014 and 2017 (N = 2252). Data on substance use (i.e., alcohol, illicit drugs, and tobacco) were from a health assessment tool mandated by Medicaid. Semi-structured interviews with 12 providers (i.e., pediatricians, nurse practitioners, behavioral health clinicians) elicited information about the current clinic workflow for adolescent substance use and barriers and facilitators to SBIRT implementation. Results Of 1588 adolescents who completed the assessment (70.5%), 6.8% reported current substance use. Self-reported use was highest among non-Hispanic Black (15.2%) adolescents and those with co-occurring depressive symptoms (14.4%). Provider-reported challenges to implementing SBIRT included a lack of space for confidential screening and a lack of referral options. Providers favored implementing technology-based tools such as tablets for adolescent pre-visit screening and electronic medical record–based decision support to facilitate brief intervention and treatment referrals. Conclusions This study fills a substantial research gap by examining factors that impede and support SBIRT implementation in pediatric FQHC settings. Successful SBIRT implementation in these settings could significantly reduce the unmet need for substance use treatment among uninsured and publicly insured adolescents. Pediatric primary care and urgent care providers perceived SBIRT to be feasible, and health information and digital technologies may facilitate the integration of SBIRT into clinic workflows. Ensuring confidentiality for screening and expanding referral options for adolescents in need of community-based addiction treatment are also critical to increasing SBIRT uptake.
Article
Background Cannabis is the illegal drug most frequently used by Minors in Austria. Due to the gradual decriminalization and legalization that has taken place in many European countries in recent years, the ÖGKJP would like to take a balanced and scientifically based stand on the complex issue of cannabis use and abuse among young people.Methods The authors searched the medline for current studies using searches tailored to each specific subtopic. Furthermore, recognized compendiums were quoted.ResultsWhile occasional recreational use of cannabis in adults with completed brain maturation and no risk profile for mental disorders is likely to be relatively harmless, early initiation of use with regular use and the increasingly available, highly potent cannabis varieties can lead to explicit and sometimes irreversible neurocognitive brain dysfunction.Conclusion Legalisation of cannabis consumption for minors needs to be objected to due to the risks of the expected damage in the area of brain development. At the same time, however, it is important to establish sensible legal regulations in order to be able to adequately counteract the fact that over 30% of all European young people occasionally consume cannabis. We are also clearly recommending to not criminalize cannabis users and provide necessary support to vulnerable and addicted cannabis users.
Article
Background Recreational and medical legalization of cannabis or marijuana use in countries and states continues to increase. Young adults aged 16–24 years have the highest prevalence rates of cannabis use. Young driver cannabis use is an incompletely understood traffic safety issue. Objectives The purposes of this scoping review were to characterize the predictors of driving under the influence of cannabis (DUIC) among healthy young drivers and to identify research gaps. Inclusion criteria A self-reported measure of DUIC and a correlation (r, odds ratio, risk ratio) to demographic or behavioral variables such as age, gender and frequency of use was required for inclusion Sources of evidence APA PsycInfo, SPORTDiscus, Academic Search Complete, Google Scholar, MEDLINE Complete, Scopus, Embase, ERIC, TRID and POPLINE databases were searched using an a priori protocol. Methods The PRISMA-ScR methods and checklist were used to conduct the scoping review. After the removal of duplicates, abstract screening (N = 999), and full-text review (N = 173), 19 primary studies met inclusion criteria. Predictors were coded and mapped into four primary thematic categories: social, individual, driving and substance use. Results Of the included studies, a total of 52,197 respondents were surveyed in-person or online and 51.8 percent were males. The predominant predictors of DUIC included being a male, high school senior, with lower grades, having a younger ‘age of first cannabis use’, a higher frequency of consumption, a reduced perception of danger, repeatedly binge drinking, a history of driving under the influence of alcohol and living with fewer parents. Research gaps Identified research gaps include methods used to study young drivers, cannabis edibles, chronic user tolerance, driver adaptation, passengers of drivers who consumed cannabis, combined use with other legal and illicit drugs, and combined smartphone and cannabis use. Conclusion The results of this scoping review can be used to develop and target general and specific predictors of DUIC in novice, teen and young drivers. Additional research designs will be required to gain a more complete evidence-based understanding of the effects of cannabis on young drivers.
Article
Background There is a paucity of prospective longitudinal studies examining the associations between maternal use of alcohol and tobacco during pregnancy and the risk of cannabis use in offspring. The aim of this study was to examine the association between prenatal alcohol and tobacco exposures and offspring cannabis use. Methods Data were from the Raine Study, a longitudinal prospective birth cohort based in Western Australia. Cannabis use at 17 years of age was measured with a self-reported questionnaire developed to capture risky behaviors in adolescents. Associations between prenatal alcohol and tobacco exposures and the risk of cannabis use in offspring were examined using log-binomial regression models, computing relative risk (RR). We also computed the E-values (E) to estimate the extent of unmeasured confounding. Results After adjusting for potential confounders, we observed increased risks of cannabis use in offspring exposed to first trimester prenatal alcohol use (RR = 1.38, 95% CI: 1.09–1.75; E = 2.10, CI:1.40) and tobacco use (RR = 1.42, 95% CI: 1.08–1.86; E = 2.19, CI:1.37) as well as third trimester prenatal alcohol use (RR = 1.39, 95% CI: 1.09–1.79; E = 2.13, CI:1.40) and tobacco use (RR = 1.39, 95% CI: 1.09–1.79; E = 2.21, CI:1.34]. We also noted dose-response associations in which risk estimates in offspring increased with the level of exposures to prenatal alcohol and tobacco use. Conclusion These findings provide epidemiological evidence for effects of prenatal alcohol and tobacco exposures on offspring cannabis use. Although these results should be confirmed by other studies, the present study adds to the mounting evidence suggesting that women should be encouraged to abstain from alcohol and tobacco during pregnancy.
Article
Background: Historically substance use literature has focused on smoking as the main mode of cannabis consumption, so there are knowledge gaps surrounding current understanding of edibles and vaping. These alternative modes of cannabis use are already common among Canadian youth; however, little is known about how these cannabis use patterns change over time. Methods: This study examined the mode (smoking, eating/drinking, vaping) and frequency of cannabis use among a large sample of Canadian youth who participated in 2017–2018 and 2018–2019 data collection waves of the COMPASS study. Using latent transition analysis, this sample consisting of 18,824 youth in grades 9–12 were categorized into cannabis use classes stratified by sex, and their transition between these classes over the one-year period was examined. Results: Three cannabis use classes were identified (occasional multimode, regular multimode, and smoking) alongside one nonuse class. Among youth who reported cannabis use at baseline, transitioning to a multimode group, and/or increasing frequency of multimode use was likely over the one-year period. Conclusions: These findings may highlight a key leverage point for harm-reduction strategies which aim to prevent cannabis related harms associated with high frequency use.
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To examine associations between cannabis use in adolescence (at age 18) and unemployment and social welfare assistance in adulthood (at age 40) among Swedish men. Longitudinal cohort study. 49 321 Swedish men born in 1949-1951, who were conscripted to compulsory military service at 18-20 years of age. All men answered two detailed questionnaires at conscription and were subject to examinations of physical aptitude psychological functioning and medical status. By follow-up in national databases, information on unemployment and social welfare assistance was obtained. Individuals who used cannabis at high levels in adolescence had increased risk of future unemployment and of receiving social welfare assistance. Adjusted for all confounders (social background, psychological functioning, health-behaviors, educational level, psychiatric diagnoses), an increased relative risk (RR) of unemployment remained in the group reporting cannabis use >50 times (RR = 1.26 CI 1.04-1.53, 95%) only. For social welfare assistance, RR in the group reporting cannabis use 1-10 times was 1.15 (CI 1.06-1.26, 95%), RR for 11-50 times was 1.21 (CI 1.04-1.42, 95%), and RR for >50 times was 1.38 (CI 1.19-1.62, 95%). Heavy cannabis use among Swedish men in late adolescence appears to be associated with unemployment and being in need of social welfare assistance in adulthood. These associations are not fully explained by other health-related, social or behavioral problems. This article is protected by copyright. All rights reserved.
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Introduction: Substance use is associated with common mental health disorders, but the causal effect of specific substances is uncertain. We investigate whether adolescent cannabis and cigarette use is associated with incident depression and anxiety, while attempting to account for confounding and reverse causation. Methods: We used data from ALSPAC, a UK birth cohort study, to investigate associations between cannabis or cigarettes (measured at age 16) and depression or anxiety (measured at age 18), before and after adjustment for pre-birth, childhood and adolescent confounders. Our imputed sample size was 4561 participants. Results: Both cannabis (unadjusted OR 1.50, 95% CI 1.26, 1.80) and cigarette use (OR 1.37, 95% CI 1.16, 1.61) increased the odds of developing depression. Adjustment for pre-birth and childhood confounders partly attenuated these relationships though strong evidence of association persisted for cannabis use. There was weak evidence of association for cannabis (fully adjusted OR 1.30, 95% CI 0.98, 1.72) and insufficient evidence for association for cigarette use (fully adjusted OR = 0.97, 95% CI 0.75, 1.24) after mutually adjusting for each other, or for alcohol or other substance use. Neither cannabis nor cigarette use were associated with anxiety after adjustment for pre-birth and childhood confounders. Conclusions: Whilst evidence of association between cannabis use and depression persisted after adjusting for pre-term and childhood confounders, our results highlight the difficulties in trying to estimate and interpret independent effects of cannabis and tobacco on psychopathology. Complementary methods are required to robustly examine effects of cannabis and tobacco on psychopathology.
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The relationship between the socioeconomic status (SES) of peers and individual academic achievement was examined in this study. This question was investigated while a variety of sociodemographic factors were being controlled, including a student's own SES. Student SES was measured by using participation in the federal free/reduced–price lunch program as an indicator of poverty status, and parental educational and occupational background as a measure of family social status. These measures were aggregated to the school level to define the SES of the peer population. Student achievement is a factor score of the three 10th–grade components of the Louisiana Graduation Exit Examination. Peer family social status in particular does have a significant and substantive independent effect on individual academic achievement, only slightly less than an individual's own family social status.
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Aims: To investigate the relationship between cannabis and tobacco use by age 15 and subsequent educational outcomes. Design: Birth cohort study. Setting: England. Participants: The sample was drawn from the Avon Longitudinal Study of Parents and Children; a core sample of 1155 individuals had complete information on all the variables. Measurements: The main exposures were cannabis and tobacco use at age 15 assessed in clinic by computer-assisted questionnaire and serum cotinine. The main outcomes were performance in standardized assessments at 16 [Key Stage 4, General Certificate of Secondary Education (GCSE)] in English and mathematics (mean scores), completion of five or more assessments at grade C level or higher and leaving school having achieved no qualifications. Analyses were sequentially adjusted for multiple covariates using a hierarchical approach. Covariates considered were: maternal substance use (ever tobacco or cannabis use, alcohol use above recommended limits); life course socio-economic position (family occupational class, maternal education, family income); child sex; month and year of birth; child educational attainment prior to age 11 (Key Stage 2); child substance use (tobacco, alcohol and cannabis) prior to age 15 and child conduct disorder. Findings: In fully adjusted models both cannabis and tobacco use at age 15 were associated with subsequent adverse educational outcomes. In general, the dose-response effect seen was consistent across all educational outcomes assessed. Weekly cannabis use was associated negatively with English GCSE results [grade point difference (GPD), -5.93, 95% confidence interval (CI) = -8.34, -3.53] and with mathematics GCSE results (GPD, -6.91, 95% CI = -9.92, -3.89). Daily tobacco smoking was associated negatively with English GCSE (GPD, -11.90, 95% CI = -13.47, -10.33) and with mathematics GCSE (GPD, -16.72, 95% CI = -18.57, -14.86). The greatest attenuation of these effects was seen on adjustment for other substance use and conduct disorder. Following adjustment, tobacco appeared to have a consistently stronger effect than cannabis. Conclusions: Both cannabis and tobacco use in adolescence are associated strongly with subsequent adverse educational outcomes. Given the non-specific patterns of association seen and the attenuation of estimates on adjustment, it is possible that these effects arise through non-causal mechanisms, although a causal explanation cannot be discounted. © 2015 Society for the Study of Addiction.
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Longitudinal studies reporting the association between cannabis use and developing depression provide mixed results. The objective of this study was to establish the extent to which different patterns of use of cannabis are associated with the development of depression using meta-analysis of longitudinal studies. Method Peer-reviewed publications reporting the risk of developing depression in cannabis users were located using searches of EMBASE, Medline, PsychINFO and ISI Web of Science. Only longitudinal studies that controlled for depression at baseline were included. Data on several study characteristics, including measures of cannabis use, measures of depression and control variables, were extracted. Odds ratios (ORs) were extracted by age and length of follow-up. After screening for 4764 articles, 57 articles were selected for full-text review, of which 14 were included in the quantitative analysis (total number of subjects = 76058). The OR for cannabis users developing depression compared with controls was 1.17 [95% confidence interval (CI) 1.05-1.30]. The OR for heavy cannabis users developing depression was 1.62 (95% CI 1.21-2.16), compared with non-users or light users. Meta-regression revealed no significant differences in effect based on age of subjects and marginal difference in effect based on length of follow-up in the individual studies. There was large heterogeneity in the number and type of control variables in the different studies. Cannabis use, and particularly heavy cannabis use, may be associated with an increased risk for developing depressive disorders. There is need for further longitudinal exploration of the association between cannabis use and developing depression, particularly taking into account cumulative exposure to cannabis and potentially significant confounding factors.
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This study compared the adequacy of 5 theories to predict dropping out of high school before the 10th grade. These theories include full mediation by academic achievement and direct effects related to general deviance, deviant affiliation, family socialization, and structural strains. Nested latent variable models were used to test these theories on prospective data from an ethnically diverse urban sample. Poor academic achievement mediated the effect of all independent factors on school dropout, although general deviance, bonding to antisocial peers, and socioeconomic status also retained direct effects on dropping out. Therefore, none of the theories tested was fully adequate to explain the data, although partial support was obtained for each theory. Implications for prevention of early high school dropout are discussed.
Article
The creation of economically mixed communities has been proposed as one way to improve the life outcomes of children growing up in poverty. However, whether low-income children benefit from living alongside more affluent neighbors is unknown. Prospectively gathered data on over 1,600 children from the Environmental Risk (E-Risk) Longitudinal Twin Study living in urban environments is used to test whether living alongside more affluent neighbors (measured via high-resolution geo-spatial indices) predicts low-income children's antisocial behavior (reported by mothers and teachers at the ages of 5, 7, 10, and 12). Results indicated that low-income boys (but not girls) surrounded by more affluent neighbors had higher levels of antisocial behavior than their peers embedded in concentrated poverty. The negative effect of growing up alongside more affluent neighbors on low-income boys' antisocial behavior held across childhood and after controlling for key neighborhood and family-level factors. Findings suggest that efforts to create more economically mixed communities for children, if not properly supported, may have iatrogenic effects on boys' antisocial behavior. © 2015 Association for Child and Adolescent Mental Health.
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AimsTo examine changes in the evidence on the adverse health effects of cannabis since 1993.MethodsA comparison of the evidence in 1993 with the evidence and interpretation of the same health outcomes in 2013.ResultsResearch in the past 20 years has shown that driving while cannabis-impaired approximately doubles car crash risk and that around one in 10 regular cannabis users develop dependence. Regular cannabis use in adolescence approximately doubles the risks of early school-leaving and of cognitive impairment and psychoses in adulthood. Regular cannabis use in adolescence is also associated strongly with the use of other illicit drugs. These associations persist after controlling for plausible confounding variables in longitudinal studies. This suggests that cannabis use is a contributory cause of these outcomes but some researchers still argue that these relationships are explained by shared causes or risk factors. Cannabis smoking probably increases cardiovascular disease risk in middle-aged adults but its effects on respiratory function and respiratory cancer remain unclear, because most cannabis smokers have smoked or still smoke tobacco.Conclusions The epidemiological literature in the past 20 years shows that cannabis use increases the risk of accidents and can produce dependence, and that there are consistent associations between regular cannabis use and poor psychosocial outcomes and mental health in adulthood.
Article
Background Debate continues about the consequences of adolescent cannabis use. Existing data are limited in statistical power to examine rarer outcomes and less common, heavier patterns of cannabis use than those already investigated; furthermore, evidence has a piecemeal approach to reporting of young adult sequelae. We aimed to provide a broad picture of the psychosocial sequelae of adolescent cannabis use. Methods We integrated participant-level data from three large, long-running longitudinal studies from Australia and New Zealand: the Australian Temperament Project, the Christchurch Health and Development Study, and the Victorian Adolescent Health Cohort Study. We investigated the association between the maximum frequency of cannabis use before age 17 years (never, less than monthly, monthly or more, weekly or more, or daily) and seven developmental outcomes assessed up to age 30 years (high-school completion, attainment of university degree, cannabis dependence, use of other illicit drugs, suicide attempt, depression, and welfare dependence). The number of participants varied by outcome (N=2537 to N=3765). Findings We recorded clear and consistent associations and dose-response relations between the frequency of adolescent cannabis use and all adverse young adult outcomes. After covariate adjustment, compared with individuals who had never used cannabis, those who were daily users before age 17 years had clear reductions in the odds of high-school completion (adjusted odds ratio 0·37, 95% CI 0·20–0·66) and degree attainment (0·38, 0·22–0·66), and substantially increased odds of later cannabis dependence (17·95, 9·44–34·12), use of other illicit drugs (7·80, 4·46–13·63), and suicide attempt (6·83, 2·04–22·90). Interpretation Adverse sequelae of adolescent cannabis use are wide ranging and extend into young adulthood. Prevention or delay of cannabis use in adolescence is likely to have broad health and social benefits. Efforts to reform cannabis legislation should be carefully assessed to ensure they reduce adolescent cannabis use and prevent potentially adverse developmental effects. Funding Australian Government National Health and Medical Research Council.
Article
Several 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. Here 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. We 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. Our 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.