Effects of Adolescent Cannabis Use on Motivation and Depression: a Systematic Review

Summary & key facts

This review looked at 28 studies about cannabis use that started before age 18 and how it relates to motivation and depression. Heavy adolescent cannabis use was linked to worse school outcomes and higher levels of depressive symptoms. The evidence that cannabis causes a broad loss of motivation is weak, partly because few studies measured motivation directly or ruled out other factors like tobacco, alcohol, or existing depression. Brain imaging studies suggest cannabis use may be tied to changes in reward-related brain systems, but the timing and cause of these changes are not clear.

Key facts:

• The review included 28 peer‑reviewed human studies published since 2014 that examined non‑acute effects of cannabis use beginning before age 18.
• Heavy or frequent cannabis use in adolescence was associated with poorer educational outcomes (for example, lower grades, lower rates of high school completion, and reduced likelihood of post‑secondary degree attainment in some studies).
• Several studies reported higher levels of depressive symptoms among adolescents who used cannabis heavily or chronically, suggesting an association between adolescent cannabis use and increased depressive symptoms.
• Only one recent study in adolescents directly tested self‑reported general motivation and found no support for an “amotivational syndrome” after controlling for demographics, other substance use, and mental health issues.
• Neuroimaging studies in the review reported links between cannabis use and reduced dopamine synthesis capacity and reduced reward sensitivity in corticostriatal brain regions—findings the authors say are consistent with possible changes to
• Many studies varied in how they measured motivation and depression and often did not fully control for other substance use (like tobacco or alcohol) or for preexisting depression, so it is hard to separate direct cannabis effects from other
• The authors note that 6.5% of U.S. adolescents ages 12–17 reported past‑year cannabis use in 2017, and they highlight that adolescence is a time of brain development that could make youth more vulnerable to substance effects.
• The review concludes that while heavy adolescent cannabis use is linked to worse academic outcomes and more depressive symptoms, it remains unclear whether cannabis causes long‑term reductions in general motivation, and more studies that me

Topics

Bipolar Disorder and Treatment Cannabis and Cannabinoid Research Substance Abuse Treatment and Outcomes

Categories

Health Sciences Medicine Pharmacology

Tags

Affect (linguistics) Cannabidiol Cannabis Clinical psychology Cognition Communication Depression (economics) Depressive symptoms Developmental psychology Economics Effects of cannabis Macroeconomics Psychiatry Psychology Substance use

Substances

Cannabis

Conditions & symptoms

Depression Substance abuse disorder Lack of energy or motivation Sadness or low mood