Neuroimaging shows cannabis and alcohol use during adolescence alters brain structure and function, with some cognitive deficits resolving after short-term abstinence while attentional deficits persist.
Read this if you are a teen, parent, or educator who wants to understand how cannabis and alcohol affect the developing brain differently from the adult brain.
Attentional deficits persisted after abstinence while other cognitive effects resolved
What the researchers found
This review examined how cannabis and alcohol affect the adolescent brain during a period when white and grey matter are still maturing and sex hormones are driving structural changes.
Neuroimaging studies revealed differences in brain development between substance-using and non-using adolescents, including altered white matter myelination and grey matter volumes. The effects appeared related to the ongoing developmental processes that cannabis and alcohol disrupt.
An important distinction emerged: some associations between substance use and brain differences appeared to resolve after short-term abstinence, suggesting they may be temporary pharmacological effects. However, attentional deficits appeared to persist even after abstinence, suggesting more lasting impact on attention-related brain circuitry.
The review also noted sexually dimorphic features in brain development, suggesting that cannabis and alcohol may affect male and female adolescent brains differently.
Why it matters
Understanding which effects are temporary versus persistent helps prioritize prevention messages and guide clinical decisions. The finding that attentional deficits persist while other deficits may resolve suggests attention systems are particularly vulnerable during adolescent development.
The numbers in context
The review synthesizes neuroimaging and neuropsychological data but does not report pooled statistics.
How the study worked
Review of neuropsychological and neuroimaging studies examining the effects of cannabis and alcohol on adolescent brain development, including structural MRI, functional MRI, and neurocognitive assessment data.
What this study cannot tell us
Review does not present systematic methodology or quality assessment. Most neuroimaging studies are cross-sectional, making it difficult to separate pre-existing differences from substance-caused changes. The combined review of cannabis and alcohol may obscure substance-specific effects.
How to read the evidence
Narrative review of neuroimaging and neuropsychological evidence. Moderate because it synthesizes substantial imaging data but lacks systematic methodology.
When this study was published
Published in 2017.
The bigger picture
Adolescence is a critical neurodevelopmental window with ongoing myelination and synaptic pruning. The persistence of attentional deficits suggests that cannabis and alcohol may disrupt specific developmental processes that cannot be fully recovered even after discontinuation.
Questions still open
- Do the persistent attentional deficits eventually resolve with longer abstinence? Are there critical sub-periods within adolescence where exposure is most damaging? Would CBD-only exposure show the same effects as THC-containing cannabis?
Common questions
Can the teen brain recover from cannabis use?
Does cannabis affect male and female teen brains differently?
Read the original research
Cannabis and alcohol use, and the developing brain.
Behavioural brain research, 325(Pt A), 44-50
Citation
Meruelo, A D; Castro, N; Cota, C I; Tapert, S F. (2017). Cannabis and alcohol use, and the developing brain.. Behavioural brain research, 325(Pt A), 44-50. https://doi.org/10.1016/j.bbr.2017.02.025
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