Impact of Cannabinoids Across the Lifespan (ICAL)
We are a NIDA P50 center whose mission is to address the long-term effects of adolescent exposure to cannabinoids.
Human adolescence is marked by sweeping physical, emotional, and cognitive changes. One of its most recognizable features is a heightened propensity for risk-taking behaviors, which can manifest in forms as varied as engaging in dangerous driving, participating in extreme sports, or experimenting with mind-altering substances. Among these substances, cannabis arguably captivates the curiosity of teenagers more than any other. For example, data from the 2023 Monitoring the Future survey show that almost one-third of 12th-grade students in the United States used the drug at least once in the previous year, with about 12% reporting daily use for a month or longer [1]. While teenage cannabis use raises concern among parents, educators, and policymakers, understanding its risks against the backdrop of adolescent development is crucial.
During this period of sexual maturation and rapid physical growth, forebrain structures involved in higher-order mental functions – cognition, decision-making, social behavior, etc. – also undergo pronounced structural changes. Well into young adulthood, between 20- and 25-year-old in humans, neuronal networks and glial cell populations within these structures retain part of their earlier developmental plasticity making them exquisitely sensitive to environmental influences that interfere with brain neurotransmission, including trauma, stress, and neuroactive substance use. Cannabis belongs in this category because its mind-altering constituent, Δ9-tetrahydrocannabinol (THC), produces its effects by engaging the endocannabinoid system, a signaling complex that contributes in unique ways to the postnatal development of the central nervous system.
Exposure to THC during the teenage years – particularly when frequent and at high doses – can interfere with activity of the endocannabinoid system wherever this system is present, including the brain, potentially leading to lasting effects on mental and physical health. Over the past 30 years, epidemiological surveys have consistently found strong associations between adolescent cannabis use and long-term impairments in cognition, mood, and psychosocial functioning which can extend into adulthood even after cessation. Additionally, persistent alterations in body mass, core metabolism, and immunity have been reported.
These findings raise a series of important questions. If the endocannabinoids are important in adolescence, as research suggests, can exposure to THC change this neurotransmitter system in a persistent way? What alterations at the level of molecules and cells underpin these changes? And, most importantly, what are their enduring consequences on learning, memory and emotion? These are some of the key questions that ICAL, with the fundamental support of the National Institute on Drug Abuse, is addressing. Answering them will directly benefit the scientific community and the public and will help establish a solid evidence-based ground for policy decisions concerning the medical and non-medical uses of cannabis.
[1] Miech, R.A., Johnston, L. D., Patrick, M. E., O’Malley, P. M., & Bachman, J. G., Monitoring the Future national survey results on drug use, 1975–2023: Secondary school students. Monitoring the Future Monograph Series. 2023, Ann Arbor, MI: Institute for Social Research, University of Michigan.