Shared genetic variants across substance use disorders implicate common neurobiological pathways, a genome-wide mixed methods study

Substance use disorders (SUDs), including alcohol, cannabis and opioid use disorders, are known to be strongly influenced by genetics. However, it has remained unclear how much of this genetic risk is shared across different substances. A new study published in General Psychiatry addresses this question by combining large-scale genome-wide association data with advanced statistical modelling, offering new insights into the shared and distinct genetic mechanisms behind these disorders. The findings suggest that substance use disorders may partly arise from overlapping biological processes, rather than completely separate disease pathways.

Using genome-wide association study data from tens of thousands of individuals of European ancestry in Europe and the USA, the researchers compared alcohol, cannabis and opioid use disorders.

The analysis identified numerous new genetic regions, including 39 for alcohol use disorder, 10 for cannabis use disorder and one for opioid use disorder, expanding the known genetic landscape of substance use disorders. Most of the implicated genes were expressed in the brain and involved in key neurobiological processes, such as gamma-aminobutyric acid and dopamine neurotransmission, opioid receptor function, myelination and cellular stress responses. These pathways are important for reward processing, behavioural regulation and vulnerability to addiction.

"Our study indicates widespread pleiotropy across SUDs. This work characterises SUDs' genetic architectures quantitatively and identifies specific implicated genetic loci," the authors noted. The high consistency in effect direction across shared genetic regions further suggests that these factors may act through common biological mechanisms, especially in cortico-striatal and limbic brain circuits involved in reward and stress regulation.

Despite these advances, the authors note that the currently identified genome-wide significant variants explain only a small part of the genetic variance in substance use disorders, highlighting the need for larger studies. The study was also limited to individuals of European ancestry, underscoring the importance of expanding future research to more diverse populations.

By combining large-scale genetic data with innovative analytical methods, this study provides a clearer picture of the shared and distinct biological foundations of substance use disorders. The findings may support future research into transdiagnostic approaches and shared biological targets for improving prevention and treatment across different forms of addiction.