Adolescent marijuana use was a significant predictor of altered BDNF levels, and this was not a pre-existing condition but developed secondary to cannabis exposure, with younger users showing different patterns than older ones.
Adolescent health researchers, neuroscientists, parents, and youth substance use counselors.
BDNF changes followed, not preceded, use
What the researchers found
Pre-existing BDNF levels did not differ between groups, but marijuana use predicted subsequent BDNF alterations (p=0.001). Younger adolescents showed BDNF increases during early/moderate use. Older adolescents had steeper BDNF increases, especially when escalating use. The findings demonstrate BDNF changes were secondary to marijuana use, not pre-existing.
Why it matters
BDNF is essential for brain development and plasticity. This is the first study to show that BDNF changes followed marijuana initiation rather than preceding it, establishing a temporal relationship suggesting causation.
The numbers in context
500 adolescents; 4 trajectory groups; pre-use BDNF similar across groups (p=0.4); marijuana use significant predictor of BDNF change (p=0.001); younger and older adolescents showed different BDNF response patterns.
How the study worked
Single-site longitudinal cohort of 500 urban healthy adolescents with repeated plasma m-BDNF measurements. Multi-method marijuana use assessment. Group-based trajectory modeling identified four groups: naive (60%), starters (14%), chronic (20%), experimenters/quitters (6%). GLM regression controlled for confounders.
What this study cannot tell us
Single-site study. Plasma BDNF may not directly reflect brain BDNF. 500 participants but small subgroups (starters 14%, quitters 6%). Cannot fully exclude all confounders. BDNF has many functions beyond brain development.
How to read the evidence
Moderate: longitudinal design establishing temporal ordering, but plasma BDNF as a proxy and single-site.
When this study was published
Published in 2019.
The bigger picture
The age-dependent BDNF response suggests the developing brain reacts differently to cannabis depending on its maturational stage. This biological mechanism could explain why younger cannabis users tend to have worse outcomes.
Questions still open
- Do BDNF levels normalize after cannabis cessation? Does the BDNF alteration pattern predict specific cognitive outcomes?
Common questions
Does marijuana change the developing brain?
Does the age of first use matter?
Read the original research
Marijuana use among adolescents is associated with deleterious alterations in mature BDNF.
AIMS public health, 6(1), 4-14
Citation
Miguez, Maria Jose; Chan, Wenyaw; Espinoza, Luis; Tarter, Ralph; Perez, Caroline. (2019). Marijuana use among adolescents is associated with deleterious alterations in mature BDNF.. AIMS public health, 6(1), 4-14. https://doi.org/10.3934/publichealth.2019.1.4
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