THC is a partial agonist at CB1 receptors, and frequent cannabis use results in downregulation of CB1 receptors with a potential to reverse with abstinence . Another main cannabinoid is cannabidiol , which is non-intoxicating . CBD has a broad range of pharmacological actions, including inhibiting the reuptake and hydrolysis of anandamide as well as multiple receptor mechanisms . The receptor mechanisms include negative allosteric modulation of CB1 receptor, partial agonist or inverse agonist action on CB2 receptor, and agonist action on transient receptor potential vanilloid 1 and serotonin 5-HT1A receptor , all of which are thought to lie behind CBD’s effects in reducing drug reward and addiction in preclinical studies . Broadly speaking, cannabis products can be divided into four categories: high-THC-concentration/sinsemilla , herbal , hash/ resin , and very high-THC cannabis concentrates In the past two decades, dramatic increases in THC concentration in cannabis products have been reported across Europe and the U.S. . For example, a large study from the U.S. found a general increase in THC concentration in seized cannabis plant material from about 4% in 1995 to about 12 % in 2014 , and a comprehensive study from France found a dramatic increase in THC concentration in seized cannabis resin from 10 % in 2009 to 23 % in 2016 . In line with these findings, a recent study found an alarming 3-fold increase in THC concentration in seized cannabis resin in Denmark from 8% in 2000 to 25 % in 2017 , which represents the highest concentration throughout Europe . During the same period several studies indicate that CBD concentrations have remained stable or even decreased; in the studies from France and Denmark, CBD concentration remained stable at around 4% and 6% .
This development is highly concerning, as emerging studies show that cannabis products with high THC levels and low CBD levels may have more detrimental effects on cognitive function and mental health among both young and adult users , including higher risk of cannabis-induced psychosis ,vertical grow system impairments in learning and memory , and poorer addiction outcomes . Increasing THC levels have also been linked with increases in admission to CUD treatment in Europe .For example, 18 % of youth aged 15–24 in Europe report using cannabis the past year compared to 7 % of 25− 64 year old’s . In the U.S., about 25 % of adolescents report cannabis use by age 14, and recently rates of cannabis use have started to approximate adolescent alcohol use patterns with half of adolescents now using cannabis by age 18 . Notably, the percentage of lifetime cannabis using adolescents who report frequent use are at the highest level in recent decades , reflecting a three-fold increase from the lowest reported levels in 1990–1991. Rates of CUD peak during adolescence and emerging adulthood, and the global burden of disease related to cannabis use peaks in emerging adulthood. Individuals who initiate cannabis use during adolescence experience more adverse and long-lasting cannabis-related harms . About 30 % transition into CUD , and there is an increased risk of other substance use disorders later in life . Particularly among youth, frequent cannabis use is linked with a wide range of mental health disorders, health risks, and poor psychosocial outcomes, including low life satisfaction, school dropout, lower educational and occupational achievements, behavioral and legal problems, accidents/injuries, sexually transmitted infections, and psychotic disorders during adulthood . The increased risk of adverse outcomes associated with frequent cannabis use among youth is related to the nature of the developing brain and the role of the endocannabinoid system in the neurodevelopmental maturation during adolescence . The brain continues to develop from the prenatal period through childhood and adolescence until the beginning/mid 20 s . During these developmental periods, the brain is believed to be more vulnerable to the adverse effects of neurotoxins, such as regular exposure to cannabis.
This means that the health impact and effects of cannabis, stemming from the increase in cannabis potency may pose unique risks for youth, because THC is likely to interfere with the neurodevelopmental processes influenced by the endocannabinoid system . Related to this, a study of regular cannabis users and matched controls , found that cannabis use was associated with impaired axonal connectivity in the fimbria of the hippocampus and the precuneus , and that early age of onset of regular use was associated with more severe microstructural white matter alteration. Additionally, a multisite longitudinal study in Europe found that cannabis use was associated with accelerated age-related cortical thinning between the ages of 14 and 19, predominantly in prefrontal regions with a high density of CB1 receptors . Further, studies examining response inhibition have shown that adolescents engaged in cannabis use require more neural resources to perform at the same level as non-using adolescents , or perform worse . However, longitudinal studies are required to determine if these differences are directly related to THC exposure or whether they may predispose individuals for developing CUD. In the only randomized, placebo-controlled study of cannabis administration in adolescents and adults to date , adolescents experienced heightened impairment of response inhibition and wanting more cannabis, alongside blunted subjective effects and memory impairment compared to adults. Preventing and intervening in the neurocognitive and health sequelae of early or frequent cannabis use is complex, and involves physical, psychological, medical, and cultural considerations. With regard to youth cannabis use, it is important to first consider the ways in which adolescents and emerging adults are developmentally distinct from adults in ways that have historically posed challenges to substance use prevention and treatment interventions in general . One barrier to preventing the onset and escalation of adolescent cannabis use is that across cultural contexts, experimentation with substances such as alcohol and cannabis often falls in line with cultural expectations, and is perceived as socially acceptable by the youth . However, the cultural and social context that influence an early onset of cannabis use may also have adverse neurocognitive implications for later brain and behavior function and ability . As summarized in Silvers et al. , adolescence and emerging adulthood is a period with unique neuro developmental tasks that underscore major contrasts from adulthood: myriad pubertal changes, rapidly developing cognitive skills, an emergence of self-identity, and prominent changes in the social landscape.
Accordingly, adolescent cognitive skills are also more directly tied and embedded in, and thus strongly impacted by, the socioemotional context and the broader ability to engage in self-regulatory cognitive strategies is only emerging and is markedly different from adults . Because the ability for abstract reasoning and the capacity for purposeful and planful behavior is also in a developmental neurocognitive phase, this may subsequently impact the ability to participate meaningfully in established empirically supported behavioral treatment paradigms for substance use that have historically been designed for adults and largely validated with adult samples . Exploring personal identity and a heightened sense of self also demarcates and differentiates the neurodevelopmental period of adolescence and emerging adulthood, and the formation of self-identity is itself contingent upon increased self-awareness and self-monitoring . Unique to this developmental period, enhanced self-focus and social attunement with the environment may motivate youth to use substances to improve social standing, particularly within peer contexts . In contrast to adults, adolescents may also be more likely to take risks in the presence of their peers such that risk taking in social contexts heightens the potential reward value. Of note, this penchant toward enhanced risk taking has now not only been examined as a potential risk factor, but also as a likely resilience factor, as adolescents also have an enhanced capacity to engage in prosocial “risks” when in peer contexts . Peer influence is thus a powerful motivator for both risk taking and prosocial behaviors, highlighting the significance of addressing peer interactions in adolescent prevention and treatment interventions. These central facets of neurodevelopment in adolescence and emerging adulthood highlight key contextual distinctions between youth and adult cannabis users; the assumption that adult substance prevention and treatment models work equally well for youth is itself a barrier to developing novel approaches. Another major challenge in addressing the significant public health issue that cannabis use presents for youth is that most youth who engage in frequent cannabis use do not seek or receive prevention and treatment interventions , even after years of harmful use and related negative health sequalae; on average, cannabis users have more than 10 years of near-daily use and more than 6 attempts at quitting, prior to seeking and/or receiving treatment . However, despite the high clinical importance, research on barriers to prevention and treatment interventions among youth with frequent cannabis use is surprisingly scarce, although some studies suggest that central barriers for seeking timely help involve social stigma, mobile grow systems an overall desire to be self-reliant, believing intervention is not needed, or presuming that programs will be ineffective .
Additional complicating factors involve the increasing ease of access to cannabis, particularly in regions with permissive cannabis legislation , which has been directly tied to increases in youth cannabis use , perceiving cannabis use as harmless , and increasing social acceptance of cannabis use among peers . Moreover, positive associations with cannabis coupled with limited experience of, and anticipation for, negative consequences among adolescents and emerging adults, mean that this age group might not have a sensation of urgency to seek intervention either on the personal side or on the social side. Related, once successfully engaged in prevention and treatment interventions for CUD, a significant challenge is retaining youth in the intervention . Further, the recent National Academies on Cannabis report also underscored the additional challenge of potential increase in other substance use. Taken together, to reach and help youth with/at-risk of developing CUD at an earlier stage, there is a dire need to develop and test new prevention and treatment interventions that are articulated specifically for this important neurodevelopmental population. Psychosocial interventions for cannabis use can be employed at different stages prior to and into the development of CUD and have been assessed both in non-treatment seeking youth and in youth enrolled in treatment. In particular, an important avenue for circumventing treatment barriers and reaching non-treatment seekers, and maximizing prevention and treatment impact, is via brief, early evidence-based interventions that are non-judgmental and affirming . Motivational interviewing is very well-suited to this end, because it is, by definition, non-judgmental, strength-based, affirming, empathic, and bolsters motivation for change , and has shown to be highly acceptable and feasible among young cannabis users . Prior studies have found that 2 sessions of MI can successfully reach and engage non-treatment-seeking young cannabis users and reduce cannabis use and related symptoms . However, compared to adults, effects of MI have generally been less impactful among youth . Combining brief, evidence-based psychological interventions like MI with safe and effective pharmacological treatment may represent an important avenue for reaching and engaging non-treatment seeking youth, helping them reduce or quit cannabis use, and facilitate a healthier trajectory. Multiple psychosocial interventions have been investigated for adolescents and emerging adults enrolled in CUD treatment, however these interventions have typically been developed for use in adult populations and not for cannabis as the primary problem drug .
Several reviews provide in-depth details on the nature and efficacy of each intervention approach , but examples include that the combination of MI and cognitive behavioral therapy is associated with reduced cannabis use in adolescents with CUD. Typically, MI is employed over one or two sessions initially, in order to increase motivation to stop using cannabis and enhance ambivalence towards reducing use. This is followed by several sessions of CBT, with the aim of introducing coping skills that can be used in real-life settings and include devising plans for specific high-risk situations and developing problem solving skills. Recent studies have also shown that adding vouchers or monetary incentives for not using cannabis to weekly MI + CBT in youth has been associated with increased abstinence from cannabis and increased treatment retention compared to weekly MI + CBT alone. Finally, some studies on multidimensional family therapy , an approach that involves both the adolescent and the family member, have found that MDFT has comparable efficacy to CBT over 5-6 months of treatment, with evidence of increased treatment acceptability , and that a 6-month programme has been associated with good retention as well as reduced cannabis dependence compared to individual psychotherapy .