Mice carrying a schizophrenia-associated gene mutation showed greater emotional memory deficits when exposed to THC during adolescence than either factor alone.
Read this if you're interested in why some young people may be more vulnerable to cannabis effects than others.
Synergistic memory deficits in mice with both DISC1 mutation and adolescent THC
What the researchers found
Researchers studied mice carrying a mutation in the DISC1 gene (disrupted in schizophrenia 1) to test whether adolescent THC exposure interacts with genetic vulnerability to worsen adult brain function. Mice with the DN-DISC1 mutation already showed mild memory deficits, but chronic adolescent THC treatment significantly worsened fear-associated memory in adulthood.
At the molecular level, cannabinoid CB1 receptor expression was reduced in the prefrontal cortex, hippocampus, and amygdala by either the gene mutation or THC exposure independently. When combined, THC and the mutation produced a synergistic reduction in neural activity during fear memory retrieval in these brain regions.
The results demonstrated a gene-environment interaction: the genetic risk factor made the brain more vulnerable to adolescent cannabis exposure, producing deficits that persisted into adulthood.
Why it matters
This study provides mechanistic evidence for the gene-environment interaction hypothesis in psychiatric illness. It suggests that adolescents carrying certain genetic variants may be disproportionately vulnerable to lasting cognitive effects from cannabis, which has implications for understanding differential risk.
The numbers in context
CB1 receptor expression was reduced in 3 key brain regions (prefrontal cortex, hippocampus, amygdala). Synergistic reduction in c-Fos expression was observed during cue-dependent fear memory retrieval in DN-DISC1 mice with adolescent THC exposure.
How the study worked
Controlled animal study using transgenic mice expressing dominant-negative mutant DISC1. Adolescent mice received chronic THC treatment, then underwent fear conditioning and memory testing in adulthood. Brain tissue was analyzed for CB1 receptor expression and c-Fos activation patterns.
What this study cannot tell us
Animal model results do not directly translate to humans. The DISC1 mutation is one of many genetic factors linked to schizophrenia risk. THC was administered in isolation, without the other cannabinoids present in whole cannabis. Dosing patterns may not reflect human use.
How to read the evidence
Controlled animal study with transgenic mice. Findings are mechanistic and do not directly confirm human effects.
When this study was published
Published in 2015. The gene-environment interaction model continues to be investigated.
The bigger picture
Not everyone who uses cannabis as a teenager develops lasting problems, and genetics may partly explain why. This study provides animal model evidence that specific genetic variants related to schizophrenia risk can amplify the effects of adolescent cannabis exposure on brain function.
Questions still open
- Could genetic screening identify adolescents at heightened risk from cannabis use? Would CBD co-administration protect against these gene-environment interaction effects? Do these fear memory deficits map onto specific psychiatric symptoms in humans?
Common questions
Does this mean cannabis causes schizophrenia?
What is the DISC1 gene?
Read the original research
Adolescent cannabis exposure interacts with mutant DISC1 to produce impaired adult emotional memory.
Neurobiology of disease, 82, 176-184
Citation
Ballinger, Michael D; Saito, Atsushi; Abazyan, Bagrat; Taniguchi, Yu; Huang, Ching-Hsun; Ito, Koki; Zhu, Xiaolei; Segal, Hadar; Jaaro-Peled, Hanna; Sawa, Akira; Mackie, Ken; Pletnikov, Mikhail V; Kamiya, Atsushi. (2015). Adolescent cannabis exposure interacts with mutant DISC1 to produce impaired adult emotional memory.. Neurobiology of disease, 82, 176-184. https://doi.org/10.1016/j.nbd.2015.06.006
Explore the wider topic
- How to Talk to Your Teenager About Weed (Without Losing Them)
- My Kid's Friends Smoke Weed: A Parent's Guide
- I Smoke Weed But Don't Want My Kids To: Navigating the Hypocrisy
- Quitting Weed as a Parent: Why It Is the Hardest and Most Important Quit
- Quitting Weed as a Teen or Young Adult
- My Kid Is Smoking Weed: A Parent's Guide