Does chronic adolescent THC exposure represent a public mental health crisis?


Chronic adolescent exposure to THC and cannabis could lead to adverse mental health outcomes and impacted brain functioning.

“Adolescence is a critical period, with increased risk for cannabis and, in particular, high tetrahydrocannabinol (THC) potency cannabis use. This may represent a public health crisis,” Christopher J. Hammond, MD, PhD, shared with attendees of the 2021 Annual Psychiatric TimesTM World CME Conference.

In his presentation, “Impact of THC on Adolescents: Neurodevelopment,” Hammond shared that chronic adolescent THC exposure across animal and human studies is associated with disruptions or alterations in brain development. Furthermore, it is associated with adverse mental health outcomes, including depression and anxiety.

“Contrary to a lot of what the popular media messaging has communicated to us, data across studies of young people show that adolescents that use cannabis regularly and who cut down or stop using cannabis show reductions in depression and anxiety and improvements in cognition,” said Hammond.

Abstinence from cannabis for 3 to 4 weeks could reduce anxiety and depression, improve sleep, and boost cognition in adolescent regular cannabis users.1-3

Cannabis is the most commonly used federally illicit drug by US youth, and it accounts for more than 75% of teen admissions to substance use treatment. About 1.4 million adolescents try cannabis for the first time each year.4

Early onset of cannabis use, according to Hammond, could lead to a number of health issues, including major depressive disorder, alcohol use disorders, substance use disorders, suicidality, anxiety disorders, bipolar disorders, psychosis, and delinquent behaviors.5-8

“There appears to be a relatively consistent pattern of findings showing that adolescent cannabis use is associated in a dose dependent manner with poor outcomes in academic and occupational functioning, cognition, and psychiatric and substance use outcomes, and that these may be worse for young people with mental health problems,” said Hammond.

Adolescent cannabis use could also lead to potential long-term brain effects, like dysfunction in white matter tracts, altered brain waves, and decreased brain blood flow. These effects are larger and more consistent with earlier age of onset and heavy use.

“As more data comes in, we can further update and inform this field, but using the data as it exists now is important,” concluded Hammond.


1. Jacobus J, Squeglia LM, Escobar S, et al. Changes in marijuana use symptoms and emotional functioning over 28-days of monitored abstinence in adolescent marijuana users. Psychopharmacology. 2017;234(23-24):3431-3442.

2. Moitra E, Anderson BJ, Stein MD. Reductions in cannabis use are associated with mood improvement in female emerging adults. Depress Anxiety. 2016;33(4):332-338.

3. Hanson KL, Winward JL, Schweinsburg AD, et al. Longitudinal study of cognition among adolescent marijuana users over three weeks of abstinence. Addict Behav. 2010;35(11):970-976.

4. Hammond CJ, Chaney A, Hendrickson B, Sharma P. Cannabis use among U.S. adolescents in the era of marijuana legalization: a review of changing use patterns, comorbidity, and health correlates. Intl Rev Psychiatry. 2020;32(3):221-234.

5. Morgan CJ, Gardener C, Schafer G, et al. Sub-chronic impact of cannabinoids in street cannabis on cognition, psychotic-like symptoms and psychological well-being. Psychol Med. 2012;42(2):391-400.

6. Arterberry BJ, Padovano HT, Foster KT, et al. Higher average potency across the United States is associated with progression to first cannabis use disorder symptom. Drug Alcohol Depend. 2019;195:186-192.

7. DiForti M, Quattrone D, Freeman TP, et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. Lancet Psychiatry. 2019;6(5):427-436.

8. Hines LA, Freeman TP, Gage SH, et al. Association of high-potency cannabis use with mental health and substance use in adolescence. JAMA Psychiatry. 2020;77(10):1044-1051.

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