New study sheds light on genetic links to cannabis and psychiatric behaviors
Since the human genome was solved in 2001, genetics research has moved fast and furious.1 Piles and piles of data collected since then have revealed how much every little behavior or quirk is somehow associated to our genetic makeup. Of course one cannot dismiss the role of the environment in shaping behavior but genes play an essential role in planting the seeds that eventually develop into what makes each one of us unique.2
While this vast array of genetics data has been available to researchers (largely through pre-clinical or clinical studies), much of the world outside of science has lived on the outskirts of this information. Until, that is, genetics testing became available to the public.
Consumer genetics testing, while controversial,has widespread appeal.3Scientists are eager to identify genetic links as research moves closer to the promise of personalized medicine, and, digital-savvy consumers, now accustomed to having information at their fingertips, want to learn more about their health and play a larger role in their medical decisions.4
While there are several companies that offer a spit-in-a-cup-like service, 23 and Me has invested in application of its consumer work to genetics research by collaborating with academic and industry partners. Through these partnerships, researchers can conduct genome-wide association studies (GWAS) to identify whether certain genes are linked to individual traits using very large data sets.5
23 and Me researchers and their collaborators (which include the International Cannabis Consortium) recently explored a key issue regarding the link between cannabis use and schizophrenia. In a study published in Nature Neuroscience, a GWAS of lifetime cannabis use was conducted using data from over 180,000 people from combined data sets.6 The analysis revealed that there is in fact a genetic relationship between cannabis use and schizophrenia (and other psychiatric behaviors) – but it’s not the link they expected to find.
Researchers found that there was weaker evidence that cannabis use caused schizophrenia and stronger evidence that having schizophrenia caused cannabis use.6
The infamous cannabis-psychosis paradox has been marred by confusion and contention for many years, with strong evidence of a correlational (but not causal) link, which prohibitionists lean on to dissuade against policy reform. The possibility that prodromal schizophrenia patients use cannabis to self-medicate for early symptoms could not previously have been teased out of this equation due to the observational nature of these studies. But new data from this study certainly add some key evidence to resolving this debate.
Data from large studies such as this may begin to shift thinking in the academic world, and, hopefully at some point, policy-making as well. However, longitudinal, observational studies with real-time, rather than prospective, data are certainly fundamental to a better understanding of how cannabis use affects the body over time and when cannabis-based therapeutics may be most effective for treating certain conditions.
- Lander, E.S., et al., “Initial Sequencing and Analysis of the Human Genome”, Nature, 2001, Volume 409.
- Plomin, R., DeFries, J.C., Knopnik, V.S., Neiderhiser, J.M., “Top 10 Replicated Findings from Behavioral Genetics”, Perspect Psychol Sci, 2016, Volume 11.
- Tandy-Connor, S., et al., “False-positive Results Released by Direct-to-Consumer Genetic Tests Highlight the Importance of Clinical Confirmation Testing for Appropriate Patient Care”, Genetics in Medicine, 2018, Epub.
4.Roberts, J.S., Ostergren J. “Direct-to-Consumer Genetic Testing and Personal Genomics Services: A Review of Recent Empirical Studies”, Curr Genet Med Rep, 2013, Volume 1.
- Gibson, G. “Population Genetics and GWAS: A Primer”, PLoS Biol, 2018, Volume 16.
6. Pasman, J.A., et al., “GWAS of Lifetime Cannabis Use Reveals New Risk Loci, Genetic Overlap with Psychiatric Traits, and a Causal Influence of Schizophrenia”, Nature Neurosci, 2018, Volume 21.