Adolescent methamphetamine and cannabis co-users had increased striatal brain volume and intensified novelty-seeking behavior compared to healthy controls.
Read this if you want to understand how adolescent drug use affects the brain's reward system.
Methamphetamine exposure correlated with both striatal volume and novelty seeking
What the researchers found
Researchers compared brain scans from three groups of adolescents: healthy controls (10), methamphetamine users (9), and combined methamphetamine plus cannabis users (8). The combined Meth+cannabis group showed increased regional striatal volume and intensified novelty seeking compared to controls.
The degree of methamphetamine exposure correlated positively with both striatal volume and novelty seeking in both drug-using groups. The striatum is a brain region central to reward processing and motivation.
The findings supported theories that the striatum plays a key role in adolescent substance abuse vulnerability, and that drug use during adolescence may further modify this brain region while it is still developing.
Why it matters
The striatum undergoes significant remodeling during adolescence. If substance use during this period enlarges or alters striatal structure, it could create a feedback loop where drug use increases reward sensitivity, which in turn increases drug-seeking behavior.
The numbers in context
Controls: n=10. Meth only: n=9. Meth+cannabis: n=8. Meth exposure positively correlated with striatal volume and novelty seeking in both drug-using groups.
How the study worked
Cross-sectional neuroimaging study using 3T MRI. Three groups of adolescents: controls (n=10), methamphetamine users (n=9), methamphetamine+cannabis users (n=8). Structural brain imaging analyzed for regional striatal morphology. Novelty seeking assessed with Cloninger's Tridimensional Character Inventory.
What this study cannot tell us
Very small sample sizes. Cross-sectional design cannot establish causation or temporal sequence. Cannot separate methamphetamine effects from cannabis effects in the co-use group. No longitudinal follow-up. Demographic differences between groups could confound results.
How to read the evidence
Cross-sectional neuroimaging study with very small groups. Preliminary findings that cannot establish causal direction.
When this study was published
Published in 2012. Adolescent brain development and substance use effects remain active areas of neuroimaging research.
The bigger picture
This study could not determine whether enlarged striata predisposed adolescents to drug use or resulted from it. Both directions are plausible: pre-existing differences in reward circuitry may increase vulnerability, and drug use may further alter the developing brain.
Questions still open
- Are striatal volume increases a cause or consequence of substance use? Does cannabis add to methamphetamine's effects on the striatum, or are these independent? Would striatal changes normalize with sustained abstinence?
Common questions
Does drug use change the teen brain?
What is novelty seeking and why does it matter?
Read the original research
Abnormal striatal circuitry and intensified novelty seeking among adolescents who abuse methamphetamine and cannabis.
Developmental neuroscience, 34(4), 310-7
Citation
Churchwell, John C; Carey, Paul D; Ferrett, Helen L; Stein, Dan J; Yurgelun-Todd, Deborah A. (2012). Abnormal striatal circuitry and intensified novelty seeking among adolescents who abuse methamphetamine and cannabis.. Developmental neuroscience, 34(4), 310-7. https://doi.org/10.1159/000337724
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