Marijuana is the most commonly used illicit drug in the United States and worldwide. Initiation of use typically occurs during adolescence. The most recent epidemiological data indicate that in the United States, 42% of high school seniors have tried marijuana, 18% have used it in the past 30 days, and 5% use it daily.1 Among adolescents aged 12 to 17, 3.6% met criteria for cannabis use disorder (abuse or dependence) and 2% met criteria for cannabis dependence.2
More than half (51%) of adolescents reported that marijuana is fairly or very easy to obtain.2 This ease of availability may have contributed to a recently reported "reverse gateway" from marijuana use to cigarette use to nicotine(Drug information on nicotine) dependence.3,4 The initial age of first marijuana use has been declining,5,6 and there is evidence to indicate that earlier initiation is associated with problem- related marijuana use, "hard" drug use, polydrug use, and academic failure.7 Positive subjective response to marijuana during early adolescence, independent of potentially confounding factors, is a strong risk factor for the development of cannabis dependence in young adulthood.8 Adolescent marijuana use is also associated with impaired driving9,10 and delinquent behavior.11,12 Using marijuana once per week or more during adolescence is associated with a 7-fold increase in the rate of daily marijuana use in young adulthood.13
Chronic use is associated with impaired immune function,14 respiratory illnesses,15 cognitive problems,16,17 and motivational impairment.18-20 Association does not necessarily imply causation; however, there is a confluence of evidence suggesting that heavier use and earlier initiation of use are associated with generally poorer outcomes.Marijuana use and comorbidity
It has become increasingly clear that frequent marijuana use during adolescence is often associated with psychiatric disorders, although the directionality and nature of these associations has long been debated. Some argue that marijuana use can begin as "self-medication" for psychiatric disorders, while others say that habitual marijuana use can predispose some individuals to psychiatric symptoms. It is also argued that shared risk factors may predispose some adolescents to both marijuana use and psychopathology.
Social anxiety disorder in adolescence is associated with 6.5-times great- er odds of subsequent cannabis dependence developing.21 Other anxiety and major depressive disorders, however, do not appear to predispose adolescents to development of cannabis use disorders. Instead, frequent marijuana use during adolescence appears to increase the risk of subsequent development of anxiety and depressive disorders.22,23 The prevalence of cannabis use disorders is 2 to 3 times greater among adolescents who have major depression.2
Conduct disorder possesses a bidirectional relationship with marijuana use in adolescence. Conduct disorder predicts marijuana and other substance use, while early-onset marijuana use predicts conduct disorder, even when controlling for potential confounds.24-26 Marijuana use has long been known to precipitate acute psychotic symptoms in some people, and rates of marijuana use are relatively high among persons with psychotic disorders. Of significant interest, there is emerging literature supporting a causal association between adolescent marijuana use and subsequent onset of psychotic illness in those who are vulnerable.27-33 Further work is needed in this area to clarify the directionality, causality, and specificity of relationships between adolescent marijuana use and psychopathology.Treatment
Marijuana is the primary substance of abuse in most adolescent treatment admissions.34 The evidence base for treatment of adolescent marijuana use disorders is generally limited to psychosocial interventions. The most comprehensive investigation is the Cannabis Youth Treatment Study, which evaluated the effectiveness of 5 treatment arms.35 This included a combination motivational enhancement/cognitive-behavioral therapy (MET/CBT) treatment (in both 5- and 12-session formats), a family education and therapy intervention, a community reinforcement approach, and multidimensional family therapy. All modalities ex- hibited similarly modest effect sizes, with the MET/CBT and community reinforcement treatments being most cost-effective.
Contingency management, which includes rewards for marijuana abstinence, is a modality with emerging evidence in this population as well.36 Multisystemic therapy, an intensive multimodal treatment approach that incorporates individual, family, and community components, has demonstrated effectiveness among delinquent adolescents with substance use dis- orders, including cannabis abuse and dependence.37
Despite evidence that adolescent marijuana users are more likely than adults to exhibit symptoms of dependence and difficulty in quitting,38 factors contributing to continued use and relapse are not well understood in this population and may differ from those in adults.39,40 Given that the current evidence base includes only modestly effective interventions, it is important to closely investigate barriers to treatment response to develop more successful treatments.
It is commonly posited that among substances of abuse in general, craving and withdrawal symptoms are factors that commonly interfere with successful cessation of use and sustained abstinence. Indeed, multiple FDA-approved medications for substance use disorders specifically target craving, such as sustained-release bupropion for nicotine dependence and naltrexone(Drug information on naltrexone) for alcohol dependence.
In addition, medications are often used to target withdrawal from substances, such as benzodiazepines for alcohol(Drug information on alcohol) dependence and clonidine and buprenorphine(Drug information on buprenorphine) for opioid dependence. These medications have been prescribed as adjunctive interventions to be used with psychosocial interventions. It may be that treatments targeting withdrawal and craving in adolescent marijuana users could be developed to complement concurrent psychosocial treatments.