Association Between Cannabis Use and Neuropsychiatric Disorders: A Two-sample Mendelian Randomization Study.

Background: The progressive legalization and widespread use of cannabis has led to its use as a treatment for certain neuropsychiatric disorders. Traditional epidemiological studies suggest that cannabis use has an effect on some neurocognitive aspects. However, it is unclear whether cannabis use is causally related to common neuropsychiatric disorders. The present study was conducted to illustrate the causal relationships of genetically predicted cannabis use with common neuropsychiatric disorders.

Methods: We used a two-sample Mendelian randomization method using genome-wide association study (GWAS) summary statistics obtained from publicly available databases on lifetime cannabis use and 10 neuropsychiatric disorders, including multiple sclerosis (MS), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), autism spectrum disorder (ASD), epilepsy, generalized epilepsy, focal epilepsy, migraine, migraine with aura, migraine without aura, schizophrenia (SCZ), anorexia nervosa (AN), attention-deficit/hyperactivity disorder (ADHD), and Parkinson's disease (PD) were studied with a two-sample Mendelian randomization method for GWAS summary statistics. The inverse variance weighted (IVW) method was used as the main analysis model.

Results: Our study suggests that lifetime cannabis use is associated with an increased risk of developing PD (odds ratio (OR) = 1.782; 95% CI 1.032-3.075; = 0.038) and an increased risk of ADHD in female participants (OR = 1.650; 95% CI 1.051-2.590; = 0.029).

Conclusions: Cannabis intake may cause adverse effects relating to certain neuropsychiatric disorders. Therefore, special attention should be paid to the side effects of addictive drugs during clinical treatment to avoid harmful effects on the brain and neurocognition.