Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality

Molecular Psychiatry

This study shows that attention deficit hyperactive disorder (ADHD) increases the likelihood that someone will use cannabis at least once in their life. The researchers used a technique called ‘Mendelian randomization’, which allows them to go beyond simple associations and actually test whether ADHD causes cannabis use, and whether cannabis use causes ADHD.

They used two databases including over 50,000 people who had their entire genome scanned. The researchers found that ADHD increases the odds of lifetime cannabis use by somewhere between 4-16 times. They note, however, that this estimate seems high. They point out that previous research suggests the true increase in odds is likely somewhere between 1.5-5. The study also showed that cannabis use does not cause an increase in the odds of having ADHD.

ADHD and cannabis use have complex etiology. While ADHD is 70-80% determined by genetics, cannabis use is about 40-50% determined by genetics. The researcher also found four genetic sequences that were often shared between ADHD and lifetime cannabis use. 

For the original article, click here.

Soler Artigas, M., Sánchez-Mora, C., Rovira, P. et al. Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality. Mol Psychiatry (2019). https://doi.org/10.1038/s41380-018-0339-3