The Influence of Cannabis Use on Neural Connectivity Between the Nucleus Accumbens and The Prefrontal Cortex: Consequent Life Trajectories Among Adolescents
Data from the Monitoring the Future study (University of Michigan and NIDA 2016) revealed that marijuana use and abuse among adolescents has increased consistently over the past decade: 44.5% of 12th-graders report life-time usage and 6.0% report daily use within the last 30 days. The number of adolescents who consider cannabis use as “harmful” has declined in lockstep with the increased prevalence of increased cannabis use among adolescents. It is clearly established that marijuana use is associated with rising mental health problems, including depression, anxiety disorders, acute psychosis, schizophrenia and suicidality in adulthood, yet the precise mechanisms are unclear.
In this well-designed and well-powered study by Lichenstein, et al, 158 young men were recruited from the Pittsburgh Mother and Child Project (PMCP). Data regarding substance use and numerous variants, including current and previous alcohol use, were collected and analyzed; functional magnetic resonance imaging (fMRI) were attained from study participants at age 20. The stated endpoints of the investigation were to measure the influence of cannabis use on functional connectivity of the nucleus accumbens (NAc) with the prefrontal cortex and to assess psychosocial functioning two years later. Adolescent cannabis use trajectory, frequency of recent cannabis use and the participant’s age of initiation were considered important developmental factors.
Why Does This Matter?
These data and subsequent analysis suggest that different trajectories of adolescent cannabis use are associated with distinct patterns of neural reward circuit function in early adulthood. Escalating marijuana use presents a higher risk for impaired motivation, including elevated depressive symptoms, anhedonia and poor educational attainment. It follows that alterations, perhaps the degradations of the reward circuitry, represent the mechanism by which cannabis users fail to attain their potential, resulting in both developmental and dose-dependent impairment in their higher-level functioning.