The influence of early and frequent use of marijuana on the risk of desistance and of progression to marijuana-related harm

Variations of cannabis-related adverse mental health and addiction outcomes across adolescence and adulthood: A scoping review

INTRODUCTION

Evidence supporting associations between cannabis use and many health outcomes is growing, however it remains unclear how such associations vary across the lifespan. We therefore aim to answer the following questions: (1) Are the risks of cannabis's adverse effects on mental health and addiction-related outcomes different in adolescents than in adults? (2) What are the relationships between these cannabis's adverse effects and (a) an individual's age at first cannabis use, (b) age at assessment, and (c) duration of cannabis use?

METHODS

We searched Medline, Embase, CINAHL, and PsychINFO from inception to 18 October 2021. Two reviewers independently screened studies and descriptively synthesized results.

RESULTS

We included 140 studies. Cannabis effects on mental health and addiction-related outcomes were worse in adolescents, early cannabis initiators and cannabis users who consumed for longest periods. Evidence of worse long-term adverse effects in adolescents was substantial for psychosis, cannabis, and nicotine use disorders; mixed for depression, suicidality, other substance use and disorders; and limited for anxiety. Additionally, acute cannabis exposure had the opposite trend with adults more often reporting adverse effects than adolescents.

CONCLUSION

The available evidence suggests that cannabis use should be delayed as late as possible in adulthood and shortened in duration across the lifespan to decrease the risk of negative outcomes, while emphasizing the need for adapted harm reduction approaches. This scoping review provides evidence on the role of age and duration of exposure as determinants of cannabis-related adverse effects, which may inform prevention and harm reduction strategies.

SYSTEMATIC REVIEW REGISTRATION

https://doi.org/10.17605/OSF.IO/BYG72.

Literature review: Substance use screening and co-morbidity in medically hospitalized youth

OBJECTIVES

Pediatric and young adult patients frequently present to medical inpatient (MIP) units for treatment of substance use disorder (SUD). Given the risk of lifelong dependence and related complications in early life substance use (SU), a review of the literature is warranted.

METHODS

We conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) systematic review of literature published through April, 62,020, which examined incidence, screening, and complications of pediatric and young adult SU in the MIP setting.

RESULTS

8843 articles were screened, and 28 articles were included for final qualitative synthesis. The overall prevalence of SU-related discharge diagnoses ranged from 1.3% to 5% for patients aged 0 to 26 years. When compared to adult patients, nearly double the rate of co-morbid psychopathology was observed. Three studies utilized systematic screening tools, with the remainder relying on biologic screens and admission or discharge diagnoses.

CONCLUSIONS

The results of our review indicate that current screening practices for SU in the MIP clinical setting are subpar and likely result in an underestimation of incidence and morbidity due to limited use of systematic screening tools. Despite this, incidence of SU hospitalizations and related medical and psychiatric complications continue to rise.

Deleterious Effects of Ethanol, Δ(9)-Tetrahydrocannabinol (THC), and Their Combination on the Spatial Memory and Cognitive Flexibility in Adolescent and Adult Male Rats in the Barnes Maze Task

Research demonstrates that adolescents differ from adults in their response to drugs of abuse. The aim of the present study was to examine the influence of ethanol, Δ9-tetrahydrocannabinol hydrochloride (THC), and a combination of these drugs given during adolescence on spatial memory in adolescent and adult rats. Thus, adolescent rats (postnatal day (PND) 30) were subjected to the following groups: 0.9% NaCl; 1.5 g/kg ethanol; 1.0 mg/kg THC; 1.5 g/kg ethanol + 1.0 mg/kg THC. Rats received drug injection four times at three-day intervals. One day after the last injection, half of the treated animals were tested in the Barnes maze task, whereas the remaining animals were tested on PND 70. Results show that there was a significant age effect on spatial memory in the Barnes maze task after these drug administrations. Adolescent animals demonstrated more potent deficits in the spatial learning and memory (probe trial) and in cognitive flexibility (reversal learning) than did adults. However, in adult rats that received these drugs in adolescence, memory decline was observed only after ethanol and ethanol + THC administration. Thus, our results are important in understanding the deleterious impact of THC and/or ethanol abuse during adolescence on memory function across the lifespan (adolescent versus adult).

Pediatric Consultation-Liaison Psychiatry: An Update and Review

Background

In recent years, there has been an increasing burden of child and adolescent mental illness recognized in the United States, and the need for pediatric mental health care is growing. Pediatric consultation-liaison (C-L) psychiatrists are increasingly playing a role in the management of medical and psychiatric disease for pediatric patients. The field is a fast-moving one, with understanding of new neuropsychiatric disease entities; reformulation of prior disease entities; and new interdisciplinary treatments and models of care.

Methods

In this study, we aim to review recent advances in the field of pediatric C-L psychiatry, including new diagnostic entities, updated management of frequently encountered clinical presentations, and developments in systems of care.

Conclusion

The advances in pediatric C-L psychiatry are broad and serve to promote more streamlined, evidence-based care for the vulnerable population of psychiatrically ill pediatric medical patients. More work remains to determine the most effective interventions for the wide array of presentations seen by pediatric C-L psychiatrists.

Assessing the impacts of daily Cannabis versus alcohol and methamphetamines on young Australians in youth AOD treatment

BACKGROUND

Cannabis is the most widely used illicit substance by Australian young people, including those engaged with youth alcohol and other drug (AOD) systems. While recreational cannabis use in young people may be a developmental activity for some, for others, this usage becomes regular and be associated with poorer long term outcomes. This study reports on the rates of cannabis use and co-existing psychosocial complexity factors in the Youth Needs Census (2013 and 2016) where workers report on all clients in the youth AOD system, a cohort considered highly vulnerable.

METHODS

Data was examined for two rounds of data collection for the Youth Needs Census, including 823 youth AOD service engaged young people in 2016 and 1000 AOD service engaged young people in 2013, to identify usage rates, psychosocial outcomes, and changes over time.

RESULTS

Daily use of cannabis alone significantly exceeded daily usage rates for methamphetamines, alcohol, and cannabis used alongside other substances. Daily cannabis use was significantly associated with mental health problems, employment problems, education problems, family problems, and housing problems. Daily cannabis use was associated with most psychosocial complexity factors to the same extent as daily methamphetamine use and daily alcohol use, with daily cannabis users only showing lower incidence of the drug-related harm measure. Notably, daily cannabis use also increased from 2013 (47.5%) to 2016 (54.2%).

CONCLUSIONS

It is imperative that the number of individuals using cannabis is considered alongside the severity of harm when assessing the social impact of this substance. Within cannabis users engaged with the youth AOD system, who often have high levels of psychosocial complexity, cannabis is used daily by a large proportion of these youths and may play a role in negatively impacting their lives.

Age of first use, current marijuana use and driving after use among Canadian high school students

Early exposure to marijuana may have lasting effects into adulthood given that adolescence is a critical period during which most substance use is initiated. Recreational marijuana recently became legal in Canada, with a legal age of purchase set as either 18 or 19 years, depending on the province. Historically, the mean age of onset for marijuana use among youth occurs at a much younger age. The current study examined the association between age at first use of marijuana with current marijuana use patterns and driving after use among high school students. Data on 24,630 high school students (grades 9-12) were from the 2014-2015 Canadian Student Tobacco, Alcohol and Drugs Survey. We restricted our analyses to the students who reported having ever used marijuana and had data on age at first marijuana use (n = 6709). Multivariable logistic and negative binomial regressions were performed to examine the association between current marijuana use patterns and age at first marijuana use. Students with younger age at first use of marijuana had significantly higher odds of current marijuana use, a higher frequency of consumption, and were more likely to drive after use of marijuana. Effective enforcement of age restriction laws in combination with other prevention efforts may be beneficial in delaying the age of onset of marijuana until late adolescence and early adulthood.

Cannabis use patterns and motives: A comparison of younger, middle-aged, and older medical cannabis dispensary patients

INTRODUCTION

Medical cannabis is increasingly being used for a variety of health conditions as more states implement legislation permitting medical use of cannabis. Little is known about medical cannabis use patterns and motives among adults across the lifespan.

METHODS

The present study examined data collected at a medical cannabis dispensary in San Francisco, California. Participants included 217 medical cannabis patients who were grouped into age-defined cohorts (younger: 18-30, middle-aged: 31-50, and older: 51-72). The age groups were compared on several measures of cannabis use, motives and medical conditions using one-way ANOVAs, chi-square tests and linear regression analyses.

RESULTS

All three age groups had similar frequency of cannabis use over the past month; however, the quantity of cannabis used and rates of problematic cannabis use were higher among younger users relative to middle-aged and older adults. The association between age and problematic cannabis use was moderated by age of regular use initiation such that earlier age of regular cannabis use onset was associated with more problematic use in the younger users, but not among older users. Middle-aged adults were more likely to report using medical cannabis for insomnia, while older adults were more likely to use medical cannabis for chronic medical problems such as cancer, glaucoma and HIV/AIDS. Younger participants reported cannabis use when bored at a greater rate than middle-aged and older adults.

CONCLUSIONS

Findings suggest that there is an age-related risk for problematic cannabis use among medical cannabis users, such that younger users should be monitored for cannabis use patterns that may lead to deleterious consequences.

U.S. cannabis legalization and use of vaping and edible products among youth

BACKGROUND

Alternative methods for consuming cannabis (e.g., vaping and edibles) have become more popular in the wake of U.S. cannabis legalization. Specific provisions of legal cannabis laws (LCL) (e.g., dispensary regulations) may impact the likelihood that youth will use alternative methods and the age at which they first try the method - potentially magnifying or mitigating the developmental harms of cannabis use.

METHODS

This study examined associations between LCL provisions and how youth consume cannabis. An online cannabis use survey was distributed using Facebook advertising, and data were collected from 2630 cannabis-using youth (ages 14-18). U.S. states were coded for LCL status and various LCL provisions. Regression analyses tested associations among lifetime use and age of onset of cannabis vaping and edibles and LCL provisions.

RESULTS

Longer LCL duration (OR_vaping: 2.82, 95% CI: 2.24, 3.55; OR_edibles: 3.82, 95% CI: 2.96, 4.94), and higher dispensary density (OR_vaping: 2.68, 95% CI: 2.12, 3.38; OR_edibles: 3.31, 95% CI: 2.56, 4.26), were related to higher likelihood of trying vaping and edibles. Permitting home cultivation was related to higher likelihood (OR: 1.93, 95% CI: 1.50, 2.48) and younger age of onset (β: -0.30, 95% CI: -0.45, -0.15) of edibles.

CONCLUSION

Specific provisions of LCL appear to impact the likelihood, and age at which, youth use alternative methods to consume cannabis. These methods may carry differential risks for initiation and escalation of cannabis use. Understanding associations between LCL provisions and methods of administration can inform the design of effective cannabis regulatory strategies.

Alcohol, tobacco and cannabis use: Do students with mild-intellectual disability mimic students in the general population?

Education policies encourage inclusion of students with mild-intellectual disability (mild-ID) in community/school life. However, such policies potentially increase exposure to substance use. This article examines tobacco, alcohol and cannabis use among French students enrolled in special units for students with disabilities (ULIS) at mainstream junior high schools compared to those of general population of the equivalent age; and explores factors associated with substance use among ULIS students, known to present mostly mild-ID. In 2014, a questionnaire adapted from the international HBSC/WHO study was administered to 700 ULIS students (mean-age 14.2). Comparative data were gathered from 7023 junior high-school students (mean-age 13.6) in the general population. Among students <14 years-old, tobacco and alcohol use rates were similar between ULIS and general population. For students ≥14, alcohol use remained comparable, while tobacco and cannabis use were higher in general population. Among ULIS students, low perceived health/life satisfaction, divorced/separated parents and high perceived academic demands were associated with tobacco use. Bullying, not liking school very much and attending schools outside a deprived area were associated with alcohol use. Having had sexual intercourse and not perceiving one's health as excellent were associated with cannabis use. Having dated was associated with using all three substances.

A Qualitative Study of the Context of Child and Adolescent Substance Use Initiation and Patterns of Use in the First Year for Early and Later Initiators

Individuals who initiate substance use before high school are at higher risk of negative outcomes. Eighty-six young adults between the ages of 18 and 28 participated in semi-structured qualitative interviews focused on the circumstances surrounding participants’ first use of substances and their pattern of use in the year following initiation in order to investigate similarities and differences between early versus later initiators. Initiation and use among early initiators were more likely to be encouraged by poor parental monitoring or active facilitation of use by parents. Early initiators were more likely to report risky patterns of use such as daily use and using alone. The data suggest that interventions targeting this population should focus on improving parental monitoring and decreasing positive parental attitudes toward adolescent substance use and efforts to increase identification and intervention by middle school staff to reach youth from high-risk families.

Does puberty mark a transition in sensitive periods for plasticity in the associative neocortex?

Postnatal brain development is studded with sensitive periods during which experience dependent plasticity is enhanced. This enables rapid learning from environmental inputs and reorganization of cortical circuits that matches behavior with environmental contingencies. Significant headway has been achieved in characterizing and understanding sensitive period biology in primary sensory cortices, but relatively little is known about sensitive period biology in associative neocortex. One possible mediator is the onset of puberty, which marks the transition to adolescence, when animals shift their behavior toward gaining independence and exploring their social world. Puberty onset correlates with reduced behavioral plasticity in some domains and enhanced plasticity in others, and therefore may drive the transition from juvenile to adolescent brain function. Pubertal onset is also occurring earlier in developed nations, particularly in unserved populations, and earlier puberty is associated with vulnerability for substance use, depression and anxiety. In the present article we review the evidence that supports a causal role for puberty in developmental changes in the function and neurobiology of the associative neocortex. We also propose a model for how pubertal hormones may regulate sensitive period plasticity in associative neocortex. We conclude that the evidence suggests puberty onset may play a causal role in some aspects of associative neocortical development, but that further research that manipulates puberty and measures gonadal hormones is required. We argue that further work of this kind is urgently needed to determine how earlier puberty may negatively impact human health and learning potential. This article is part of a Special Issue entitled SI: Adolescent plasticity.

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

PURPOSE

Children'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.

METHODS

Prospective, 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.

RESULTS

Fathers 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.

CONCLUSIONS

This 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.

Definitions of Risky and Problematic Cannabis Use: A Systematic Review

Although cannabis is widely used, it remains unclear which consumption patterns are more likely to produce future consequences (risky/hazardous use) or current damage (problematic/harmful use). This unresolved issue contributes to cannabis public health implications. In order to facilitate further consensus, this review analyzes previously used definitions in the literature.

METHODS

This systematic review was performed following the PRISMA guidelines. Articles published before October 2015 in the Medline, Scopus-Elsevier, ISI-Web of Knowledge and Cochrane databases and fulfilling a-priori decided criteria were retrieved. Definitions in preselected websites of national and international organizations addressing drug problems were also included.

RESULTS

Definitions identified in articles (n = 46) and official websites (n = 3) widely varied from each other. Weekly cannabis use was mostly considered risky. Problematic cannabis use was mostly described with the Cannabis Abuse and Screening Test. Evidence-based definitions as well as information on quantities consumed, time-frames and special considerations for risky groups were very limited.

CONCLUSIONS

Working on official definitions is highly necessary as criteria used remain incomplete, leading to increased confusion in the field. Recommendations to improve existing definitions are given.

Racial Differences in the Transactional Relationship Between Depression and Alcohol Use From Elementary School to Middle School

OBJECTIVE

The aim of this investigation was to test hypothesized reverse prospective relationships between alcohol consumption and depressive symptomatology as a function of race among youth.

METHOD

In a two-wave prospective study, 328 European American, 328 African American, and 144 Hispanic American youth were studied at the end of fifth grade (last year of elementary school) and the end of sixth grade (first year of middle school).

RESULTS

A positive correlation was observed between alcohol consumption and depressive symptoms among all youth. However, the predictive relationship differed based on race. For European American and Hispanic American youth, depressive symptom levels at the end of elementary school predicted alcohol consumption at the end of the first year of middle school, but the converse relationship was not observed. For African American youth, the opposite pattern was found. Alcohol consumption at the end of elementary school predicted depressive symptom levels at the end of the first year of middle school, and the converse relationship was not observed.

CONCLUSIONS

These findings suggest the possibility that etiological relationships between depression and alcohol use vary by race, thus highlighting the importance of considering race when studying the risk process.

Role of parenting styles in adolescent substance use: results from a Swedish longitudinal cohort study

OBJECTIVE

Adolescent substance use is an area of concern because early substance use is associated with a higher risk of adverse outcomes. Parenting style, defined as the general style of parenting, as well as substance-specific parenting practices may influence children's substance use behaviour. The present study aims to probe the impact of parenting style on adolescent substance use.

METHOD

A cohort of 1268 adolescents (48% girls), aged 12-13 years at baseline, from 21 junior high schools was assessed in the first semester of junior high school, and then again in the last semester of the 9th grade, 32 months later. Parenting style, operationalised as a fourfold classification of parenting styles, including established risk factors for adolescent substance use, were measured at baseline.

RESULTS

Neglectful parenting style was associated with worse substance use outcomes across all substances. After adjusting for other proximal risk factors in multivariate analyses, parenting style was found to be unrelated to substance use outcomes with one exception: authoritative parenting style was associated with less frequent drinking. Association with deviant peers, delinquent behaviour, provision of alcohol by parents, and previous use of other substances were associated with substance use outcomes at follow-up.

CONCLUSIONS

The results of the present study indicate that parenting style may be less important for adolescent substance use outcomes than what has previously been assumed, and that association with deviant peers and delinquent behaviour may be more important for adolescent substance use outcomes than general parenting style.

Contextual risks linking parents' adolescent marijuana use to offspring onset

OBJECTIVE

We studied the extent to which parent marijuana use in adolescence is associated with marijuana use onset in offspring through contextual family and peer risks.

METHOD

Fathers assessed (n=93) since childhood, their 146 offspring (n=83 girls), and offspring's mothers (n=85) participated in a longitudinal study. Using discrete-time survival analysis, fathers' (prospectively measured) and mothers' (retrospective) adolescent marijuana use was used to predict offspring marijuana use onset through age 19 years. Parental monitoring, child exposure to marijuana use, peer deviance, peer marijuana use, and perceptions of parent disapproval of child use were measured before or concurrent with onset.

RESULTS

Parents' adolescent marijuana use was significantly associated with less monitoring, offspring alcohol use, the peer behaviors, exposure to adult marijuana use, and perceptions of less parent disapproval. Male gender and the two peer behaviors were positively associated with children's marijuana use onset, controlling for their alcohol use. Parents' adolescent marijuana use had a significant indirect effect on child onset through children's deviant peer affiliations and a composite contextual risk score.

CONCLUSIONS

Parents' histories of marijuana use may contribute indirectly to children's marijuana use onset through their influence on the social environments children encounter; specifically, those characterized by more liberal use norms, exposure to marijuana use and deviant and marijuana-using peers, and less adult supervision. Given that alcohol use onset was controlled, findings suggest that the contextual factors identified here confer unique risk for child marijuana use onset.

Socialization instances linked to cannabis experimentation among French teenagers

France presents one of the highest prevalence of teenagers aged 15-year-olds who report they already have experienced cannabis in Europe. Data from the French 2010 Health Behavior in School-aged Children (HSBC) survey and environmental parameters typifying schools' neighborhoods were used to study cannabis experimentation. We conducted a two-level logistic regression (clusters being schools) on 4,175 French 8th-10th graders from 156 schools. Several individual parameters were linked to cannabis experimentation. Living in a non-intact family, feeling insufficiently monitored, having poor communication with mother and being from a family with a high socio-economic status (SES) were all associated with increased risk of cannabis experimentation. At environmental level, only being in a priority education area was linked to this behavior, without explaining differences among schools.

Revisiting the concepts of risk and protective factors for understanding the etiology and development of substance use and substance use disorders: implications for prevention

Over the past 20 years we have accumulated a greater knowledge and understanding of the genetic, neurobiological, and behavioral factors that may be associated with young people initiating the use of drugs and other substances and to progressing from use to abuse and dependence. This knowledge suggests that individuals may be "predisposed" to substance use disorders (SUD) and that the actual engagement in these behaviors depends on their environmental experiences from micro to macro levels. This paper summarizes this knowledge base and supports a developmental framework that examines the interaction of posited genetic, psychological, and neurobiological "predispositions" to SUD and those environmental influences that exacerbate this vulnerability.

Efficacy of a targeted cognitive-behavioral treatment program for cannabis use disorders (CANDIS)

AIMS

To examine the efficacy, 3- and 6-month follow-up effects of a psychological treatment for older adolescents and adults with DSM-IV cannabis use disorders. The program was tailored to the needs of this patient population.

EXPERIMENTAL PROCEDURES

A randomized controlled clinical trial of 122 patients aged 16 to 44 years with DSM-IV cannabis dependence as the main substance use diagnosis was conducted. Patients were randomly assigned to either Active Treatment (AT, n = 90) or a Delayed Treatment Control group (DTC, n = 32). Treatment consisted of 10 sessions of therapy, detailed in a strictly enforced manual. Assessments were conducted at baseline, during each therapy session, at post treatment and at follow-up assessments at 3 and 6 months.

RESULTS

The treatment retention rate was 88%. Abstinence was achieved in 49% of AT patients and in 13% of those in DTC (p < 0.001; intend-to-treat (ITT) analysis). Further, AT patients improved significantly (p < = 0.001) in the frequency of cannabis use per week, addiction severity, number of disability days, and overall level of psychopathology. Program effects were maintained over a 3-month- (abstinence rate: 51%) and 6-month follow-up (45%) period.

CONCLUSION

The treatment program is effective in obtaining abstinence as well as reducing cannabis use and improves the associated social and mental health burden.

Sex and grade level differences in marijuana use among youth

A total of 54,361 students in seventh through twelfth grades completed a survey examining the impact of perceived harm of marijuana use, ease of access in obtaining marijuana, and perceived parent/peer disapproval of marijuana use on youth involvement in annual and recent marijuana use. Results indicated that 1 in 6 (16%) students used marijuana in the past year, while 1 in 10 (10%) used marijuana in the past month. Students at highest risk for marijuana use were those who felt use was not harmful/somewhat harmful, felt it was easy/very easy to access marijuana, and had parents/peers who did not disapprove of use. Findings can assist prevention specialists to more thoroughly understand how perceived harm, ease of access, and parent/peer disapproval affect marijuana use among youth. Consistent parent-child communication on marijuana use should be encouraged.

Role of individual and developmental differences in voluntary cocaine intake in rats

RATIONALE

Early-onset drug taking is associated with increased likelihood of addiction, but it is unclear whether early onset is causal in development of addiction. Many other factors are associated with increased risk of addiction and also promote early intake. Here, a rodent model is used to explore the causality of early onset in development of self-administration and addiction-like behavior and to examine factors that promote self-administration.

METHODS

We used cocaine self-administration to examine drug taking and addiction-like behavior in adolescent and adult rats a priori characterized for their locomotor responses to novelty and cocaine and behavior in the light-dark task.

RESULTS

Adolescent animals initially sought more cocaine than adults. However, as the adolescents matured, their intake fell and they did not differ from adults in terms of unreinforced lever-pressing, extinction or reinstatement behavior. For both age groups, self-administration was positively correlated with the locomotor response to novelty, the locomotor response to cocaine, and with time in light in the light-dark task. The rats that were insensitive to cocaine's locomotor effects and that spent the least time in light in the light-dark task sought the least cocaine, appearing to be "protected" from the reinforcing effects of cocaine. There was no difference between the two age groups in appearance of this "protected" phenotype.

CONCLUSIONS

These results suggest that early onset of drug taking may promote increased use, but does not promote progression to addiction-like behavior. Furthermore, protective factors, such as innate anxiety and insensitivity to cocaine's pharmacological effects, function across developmental stages.

Are adolescents more vulnerable to drug addiction than adults? Evidence from animal models

BACKGROUND AND RATIONALE

Epidemiological evidence suggests that people who begin experimenting with drugs of abuse during early adolescence are more likely to develop substance use disorders (SUDs), but this correlation does not guarantee causation. Animal models, in which age of onset can be tightly controlled, offer a platform for testing causality. Many animal models address drug effects that might promote or discourage drug intake and drug-induced neuroplasticity.

METHODS

We have reviewed the preclinical literature to investigate whether adolescent rodents are differentially sensitive to rewarding, reinforcing, aversive, locomotor, and withdrawal-induced effects of drugs of abuse.

RESULTS AND CONCLUSIONS

The rodent model literature consistently suggests that the balance of rewarding and aversive effects of drugs of abuse is tipped toward reward in adolescence. However, increased reward does not consistently lead to increased voluntary intake: age effects on voluntary intake are drug and method specific. On the other hand, adolescents are consistently less sensitive to withdrawal effects, which could protect against compulsive drug seeking. Studies examining neuronal function have revealed several age-related effects but have yet to link these effects to vulnerability to SUDs. Taken together, the findings suggest factors which may promote recreational drug use in adolescents, but evidence relating to pathological drug-seeking behavior is lacking. A call is made for future studies to address this gap using behavioral models of pathological drug seeking and for neurobiologic studies to more directly link age effects to SUD vulnerability.

Are adolescents who moderate their cannabis use at lower risk of later regular and dependent cannabis use?

AIMS

To examine whether moderation of cannabis use among adolescent cannabis users is associated with reductions in cannabis use frequency and risk of dependence in young adulthood.

DESIGN

Ten-year representative cohort study with six surveys in adolescence (mean age 14.9-17.4 years) and two in young adulthood (mean age 20.7 and 24.1 years).

PARTICIPANTS

Inception cohort of 1943 Victorian secondary school students (96% response rate), with 1520 (78% of adolescent participants) interviewed in the final wave.

MEASUREMENTS

Participants were classified into six groups according to the maximum level of adolescent use and the extent of subsequent moderation in such use: non-users, occasional to abstinence, occasional persisting, weekly to abstinence, weekly to occasional and weekly persisting. Outcome measures were weekly+ cannabis use and DSM-IV cannabis dependence at 20 and 24 years.

FINDINGS

Thirty-one per cent reported cannabis use during adolescence. Most adolescent users had moderated their use: from occasional to abstinence (71% of occasional users), weekly to abstinence or weekly to occasional (28% and 48% of weekly+ users, respectively). By age 24, both occasional use groups were at similar, elevated risk of regular and dependent cannabis use compared to non-users. Weekly+ adolescent users were at greatest risk of these outcomes, although the weekly to abstinence group exhibited lower risk than those in the weekly persisting and weekly to occasional groups, who were at similar risk.

CONCLUSIONS

While many young people have dynamic cannabis use patterns, a pattern of moderating adolescent cannabis

Trajectories of childhood aggression and inattention/hyperactivity: differential effects on substance abuse in adolescence

OBJECTIVE

Aggression and hyperactivity/inattention each are linked to risk of alcohol use disorder (AUD), but their unique contributions remain ambiguous. The present study disaggregated these two domains developmentally and examined the relation between childhood behavior trajectories and adolescent substance use.

METHOD

A total of 335 children of alcoholic and nonalcoholic fathers were studied prospectively. Parallel process latent trajectory class analysis was developed with behavioral ratings by parents and teachers of aggression and inattention/hyperactivity across ages 7 to 16. Membership in the four latent classes was used as a predictor for problem adolescence alcohol use and substance onset.

RESULTS

Youths in the four latent trajectory classes differed in number of alcohol problems at age 16: healthy class (39% of sample, mean 2.1 alcohol-related problems), inattentive/hyperactive but not aggressive (33%; mean 2.7 problems), aggressive but not inattentive/hyperactive (4%, mean 5.0 problems), and comorbid (24%; mean 4.0 problems). Survival analysis revealed that the aggressive, comorbid, and inattentive/hyperactive classes had significantly earlier onsets of drinking, drunkenness, and marijuana use than the healthy class. Illicit drug use was also significantly increased in the comorbid, aggressive, and inattentive/hyperactive classes compared to the healthy class.

CONCLUSIONS

Three levels of behavioral risk of substance abuse exist, the highest having trajectories of increased aggressive and inattentive/hyperactive problems throughout childhood, the next involving only an increased inattentive/hyperactive behavioral trajectory, and the lowest involving those with neither type of problem. Children with both inattention/hyperactivity and aggression have the greatest need for childhood intervention to prevent substance abuse in adolescence.

Adolescent cannabis users at 24 years: trajectories to regular weekly use and dependence in young adulthood

AIMS

To examine the association between cannabis use by 18 years and problematic cannabis use at 24 years, considering possible mediating and confounding factors.

DESIGN

Ten-year representative prospective study with data from six time-points in adolescence (mean age 14.9-17.4 years) and two in young adulthood (mean age 20.7 and 24.1 years)

SETTING

Victoria, Australia.

PARTICIPANTS

Inception cohort of 1943 secondary school students (95.6% response rate), with 1520 (78% of adolescent participants) interviewed in the final wave.

MEASUREMENTS

Participants reported frequency of cannabis use for the past 6 months at each time-point in adolescence (age 14-17 years). Cannabis exposure was defined as: maximum frequency of use (occasional, weekly, daily), number of waves of use (1 or 2; 3-6) and first wave of use (early use: first waves 1-3). Young adult (24 years) outcomes were: weekly+ cannabis use and DSM-IV cannabis dependence, referred to collectively as problematic use.

FINDINGS

Of those interviewed at age 24 (wave 8), 34% had reported cannabis use in adolescence (waves 1-6), 12% at a level of weekly or more frequent use; 37% of these adolescent cannabis users were using at least weekly at wave 8, with 20% exhibiting dependence. Persistent adolescent cannabis and tobacco use as well as persistent mental health problems were associated strongly with problematic cannabis use at 24 years, after adjustment for potential confounding factors.

CONCLUSIONS

Heavy, persistent and early-onset cannabis use were all strongly predictive of later cannabis problems. Even so, occasional use was not free of later problems. Where there was co-occurring tobacco use or persistent mental health problems, risks for later problem cannabis use was higher.

Early Onset Cannabis Use and Progression to other Drug Use in a Sample of Dutch Twins

One possible explanation of the commonly reported associations between early onset cannabis use and elevated risks of other illicit drug use is that early onset cannabis use increases access and availability to other drugs. It was this argument that in part motivated policy changes in the Netherlands that led to the de facto legalization of cannabis there. This study examines, using a co-twin control design, whether previously observed associations between early onset cannabis use and elevated lifetime rates of other illicit drug use would also be observed in a sample of 219 same sex Dutch twin pairs discordant for cannabis use before age 18. After adjustment for covariates, rates of lifetime party drug use (OR=7.4, 95% CI=2.3-23.4), hard drug use (OR=16.5, 95% CI=2.4-111.3), but not regular cannabis use (OR=1.3, 95% CI=0.3-5.1) were significantly elevated in individuals who reported early onset cannabis use, relative to their co-twin who had not used cannabis by age 18. The elevated odds of subsequent illicit drug use in early cannabis users relative to their non early using co-twins suggests that this association could not be explained by common familial risk factors, either genetic or environmental, for which our co-twin methodology provided rigorous control.

Combining research approaches to advance our understanding of drug addiction

Drug addiction is a complex behavior, likely to be influenced by various genes, environmental factors, and gene-gene and gene-environment interactions. Various aspects of addiction are studied by different disciplines. Animal studies are increasing insight into brain regions and genes associated with addiction. Epidemiologic studies are establishing the factors increasing risk for initiation and continuation of substance use. Twin and adoption studies are increasing our understanding of the complex mechanisms involved in substance use, including comorbidity and gene environment interaction. Finally, molecular genetic studies in humans are starting to yield some converging findings. It is argued and illustrated with examples that greater awareness of progress in other disciplines can speed up our understanding of the complex processes involved in addiction. This should help our ability to identify who is at increased risk of becoming addicted and the development of prevention and intervention strategies targeted at an individual's specific needs.

Association between early onset of cigarette, alcohol and cannabis use and later drug use patterns: an analysis of a survey in European metropolises

OBJECTIVES

The study presents data about age of onset of alcohol, cigarette and cannabis use and investigates the association between age of onset and later drug use patterns.

METHODS

Using a sample from a cross-sectional multi-site study, personal interviews were conducted with 3,503 individuals aged 12-49 years. Last-month prevalence, age of onset and associations with subsequent use patterns were investigated.

RESULTS

Having started with cannabis before the age of 16 years was associated with an odds ratio of 1.6 for heavy cannabis use. For males, the odds ratio of heavy cannabis use was 1.7, when cannabis was already initiated by the age of 16. Heavy use of ecstasy, amphetamines, hallucinogens and cocaine is associated with use of cigarettes before 13 (OR = 1.9). For males, the odds ratio was 2.2 and for women 1.9.

CONCLUSIONS

Early use of alcohol, according to this data, does not seem to be related to subsequent heavy drug use. Early onset cannabis users show increasing probabilities of heavy use patterns. Preventive intervention programs have to start earlier than school-based programs normally do and specific developmental pathways need to be addressed.

Effects of periadolescent versus adult cocaine exposure on cocaine conditioned place preference and motor sensitization in mice

RATIONALE

Age of initial exposure to addictive substances is inversely proportional to risk of developing drug dependence. There is debate, however, as to whether intake at a young age causes dependency or whether young people who experiment with addictive substances are predisposed to dependency by other factors. OBJECTIVES. We tested the relationship between cocaine exposure at two different ages in mice and the development of subsequent drug-seeking behavior to test for age-specific exposure effects.

METHODS

We performed dose-response analysis of cocaine conditioned place preference (CPP) and locomotor activity in periadolescent and adult C57Bl/6J mice. In addition, we pretreated periadolescent and adult C57Bl/6J mice with cocaine or saline in the home cage or a drug-associated context, and then examined their behavior in a biased CPP procedure in adulthood.

RESULTS

Dose-response relationships were similar between the two age groups. In the pretreatment experiments, we observed locomotor sensitization during the pretreatment in periadolescent but not adult mice. We also observed an enhanced aversion to the non-preferred side of the chamber in periadolescent mice compared to adult mice, which was alleviated by cocaine association with that side. Third, we observed that after further conditioning in adulthood, there were no pretreatment-specific effects.

CONCLUSIONS

Our results are consistent with a "vulnerable brain" hypothesis for responses to cocaine based on our findings that periadolescent mice exhibit greater locomotor sensitization to cocaine, and greater baseline anxiety responses that are alleviated by cocaine exposure compared to adult mice.

Marijuana and tobacco: a major connection?

Smoking among teens and college students is a significant public health challenge. Tobacco, marijuana, and alcohol continue to be the most commonly abused drugs by teens and young adults. Educational efforts have resulted in increased awareness of the mortality and morbidity attributed to smoking, second-hand smoke, and prenatal exposure to tobacco. Short- and long-term consequences of marijuana use are well documented in the literature, but they have received less wide spread attention. Even less well known is the relationship between these substances. Does use of one lead to use of the other? Are there synergistic and/or antagonistic effects when these substances are used together? We need answers to these questions to understand the prevalence of use and the impact of these drugs on our nations youth and young adults. The gateway theory of drug use is often used to describe the progression from using alcohol or tobacco, to marijuana, and later use of other drugs like MDMA, cocaine, and heroin. While tobacco use does commonly precede marijuana use, we propose that marijuana may be a "gateway drug" to tobacco smoking. Our research with university students is suggesting that cigarette-smoking initiation often follows or coincides with marijuana.

Early Intervention for Adolescent Substance Abuse: Pretreatment to Posttreatment Outcomes of a Randomized Clinical Trial Comparing Multidimensional Family Therapy and Peer Group Treatment

This randomized clinical trial evaluated a family-based therapy and a peer group therapy with 80 urban, low-income, and ethnically diverse young adolescents (11 to 15 years) referred for substance abuse and behavioral problems. Both treatments were outpatient, relatively brief, manual-guided, equal in intervention dose, and delivered by community drug treatment therapists. Adolescents and their parents were assessed at intake to treatment, randomly assigned to either MDFT or group therapy, and reassessed at six weeks after intake and at discharge. Results indicated that the family-based treatment (MDFT, an intervention that targets teen and parent functioning within and across multiple systems on a variety of risk and protective factors) was significantly more effective than peer group therapy in reducing risk and promoting protective processes in the individual, family, peer, and school domains, as well as in reducing substance use over the course of treatment. These results, which add to the body of previous findings about the clinical and cost effectiveness of MDFT, support the clinical effectiveness and dissemination potential of this family-based, multisystem and developmentally-oriented intervention.

Marijuana use among adolescents

More than half of US adolescents will experiment with marijuana. Of those who try marijuana more than once, approximately one third will subsequently use marijuana regularly, although most will have stopped by their late 20s. Although genetic predisposition plays the most important role in determining who will develop dependence, environmental factors influence who will initiate marijuana use. One of the challenges for prevention and treatment programs is that the immediate adverse effects of marijuana use are not extreme, and many adolescents have difficulty in making decisions based on future risks. Therefore, the consequences of leaving school early, having unprotected sex, and driving while intoxicated are often insufficient to deter adolescents from using marijuana. Thus, it is not surprising that current prevention and treatment programs have had limited success in decreasing the rates of initiation and regular use of marijuana among adolescents. However, the accumulation of data about marijuana use in adolescents has the potential to enable the development of more effective prevention and treatment programs.

Mental health of teenagers who use cannabis. Results of an Australian survey

BACKGROUND

There is concern in the community about increasing cannabis use and its potential effect on health.

AIMS

To ascertain the prevalence of cannabis use among Australian adolescents, associations with mental health problems, risk behaviours and service use.

METHOD

Examination of data from a national representative sample of households comprising 1261 adolescents aged 13-17 years. Parents completed a psychiatric interview and questionnaires while adolescents completed questionnaires.

RESULTS

One-quarter of the adolescents in the sample had used cannabis. There were no gender differences. Use increased rapidly with age, was more common in adolescents living with a sole parent and was associated with increased depression, conduct problems and health risk behaviours (smoking, drinking) but not with higher use of services.

CONCLUSIONS

Cannabis use is very prevalent. The association with depression, conduct problems, excessive drinking and use of other drugs shows a malignant pattern of comorbidity that may lead to negative outcomes.