10-Year Study Shows Adolescent Cannabis Use Linked to Different Brain Changes Than Young Adult Use | Research

The takeaway

In a 10-year prospective study of 704 participants, cannabis initiation during adolescence was associated with cortical thinning in the prefrontal cortex that persisted into adulthood, while initiation in young adulthood affected temporal and midline areas and was linked to psychotic symptoms.

Parents, young people, and policymakers interested in how age of cannabis initiation affects brain development

704 participants over ~10 years

What the researchers found

Adolescent cannabis initiation (14-19) was associated with cortical thinning in dorsolateral and ventrolateral prefrontal cortex that persisted into young adulthood and partially mediated associations with later cocaine, ecstasy, and cannabis use at age 22. Young adult initiation (19-22) was associated with thickness changes in temporal and midline areas that mediated the link to psychotic symptoms at age 22.

Why it matters

This is one of the largest and longest prospective neuroimaging studies on cannabis, with a cannabis-naive baseline eliminating reverse causation concerns. The finding that adolescent and young adult initiation affect different brain regions with different behavioral consequences has major implications for prevention messaging.

The numbers in context

704 participants; ~10 years of follow-up; 8 European sites; adolescent initiation linked to prefrontal thinning and later drug use; young adult initiation linked to temporal changes and psychotic symptoms at age 22

How the study worked

Prospective longitudinal study of 704 participants from the IMAGEN study across 8 European sites. Participants were cannabis-naive at baseline with MRI data at baseline, 5-year, and 9-year follow-up. Cannabis use assessed with ESPAD. T1-weighted MRI processed through CIVET pipeline. Mediation analyses tested brain changes as intermediaries between cannabis use and behavioral outcomes.

What this study cannot tell us

Observational design cannot definitively establish causation despite prospective baseline. Cannabis use measured by self-report. MRI measures brain structure, not function. Genetic predisposition to both cannabis use and brain changes cannot be fully ruled out.

How to read the evidence

Large prospective longitudinal study with cannabis-naive baseline, MRI data at three time points, and multi-site design

When this study was published

2023 study

The bigger picture

This study provides some of the strongest evidence yet that when you start using cannabis matters for how it affects the brain. The adolescent brain appears vulnerable in its decision-making regions (prefrontal cortex), while the young adult brain is more vulnerable in areas linked to psychosis.

Questions still open

Is there a safe age to begin cannabis use based on brain development? Could the prefrontal thinning from adolescent use be reversed with abstinence? Do these brain changes differ by THC potency or frequency of use?

Common questions

Does starting cannabis as a teenager affect the brain differently than starting in your 20s?

Yes, according to this study. Teenage initiation was associated with thinning in the prefrontal cortex (involved in decision-making) and later drug use, while starting in early adulthood affected temporal brain areas and was linked to psychotic symptoms.

Do the brain changes from teenage cannabis use go away?

In this study, the prefrontal cortex thinning associated with adolescent cannabis initiation persisted into young adulthood (age 22). Whether these changes eventually reverse was not examined.

Read the original research

Differential associations of adolescent versus young adult cannabis initiation with longitudinal brain change and behavior.

Molecular psychiatry, 28(12), 5173-5182

View on PubMed ↗Publisher’s paper ↗

Citation

Albaugh, Matthew D; Owens, Max M; Juliano, Anthony; Ottino-Gonzalez, Jonatan; Cupertino, Renata; Cao, Zhipeng; Mackey, Scott; Lepage, Claude; Rioux, Pierre; Evans, Alan; Banaschewski, Tobias; Bokde, Arun L W; Conrod, Patricia; Desrivières, Sylvane; Flor, Herta; Grigis, Antoine; Gowland, Penny; Heinz, Andreas; Ittermann, Bernd; Martinot, Jean-Luc; Martinot, Marie-Laure Paillère; Artiges, Eric; Nees, Frauke; Orfanos, Dimitri Papadopoulos; Paus, Tomáš; Poustka, Luise; Millenet, Sabina; Fröhner, Juliane H; Smolka, Michael N; Walter, Henrik; Whelan, Robert; Schumann, Gunter; Potter, Alexandra; Garavan, Hugh. (2023). Differential associations of adolescent versus young adult cannabis initiation with longitudinal brain change and behavior.. Molecular psychiatry, 28(12), 5173-5182. https://doi.org/10.1038/s41380-023-02148-2