9 1Ãâ·Ñ°æÏÂ

A groundbreaking study led by 9 1Ãâ·Ñ°æÏ researchers has produced the most comprehensive genetic map of obsessive-compulsive disorder (OCD), identifying 30 areas of the human genome linked to the debilitating mental health condition that affects up to three per cent of the world's population. 

While previous studies have shown that OCD can run in families, this is the first time researchers have discovered specific locations on a chromosome where DNA variants are associated with higher susceptibility of a particular disease or trait — data that could lead to both improved ways of identifying people who are at risk for OCD and ultimately better treatments . 

The study, published in , looked at the biological basis of OCD and showed that the risk is influenced by many genes, often the same ones involved in other psychiatric disorders.  

"Our findings confirm our believe that OCD is caused by a complex combination of environmental and genetic causes," says , a 9 1Ãâ·Ñ°æÏ Research Chair and lead senior author on the paper. "As part of this complex combination, many genomic regions contribute to the etiology of OCD, affecting a diverse group of brain regions rather than a single specific one. 

In what is the largest genetic study of OCD to date, researchers compared the DNA of more than 53,000 people with OCD to more than two million people without the disorder. This massive dataset allowed them to search for tiny differences in DNA — known as genetic variants or SNPs — that are more common in people with OCD. Ìý
 Ìý
The study identified 30 specific regions in our DNA that are associated with an increased risk of developing OCD. This marks a significant increase from previous, smaller studies. By looking closely at the identified DNA regions, scientists pinpointed 249 potential genes involved in OCD and then narrowed this down to 25 particularly strong "candidate" genes. 

After decades of fumbling in the dark, we have finally cracked the piñata of OCD genetics

"After decades of fumbling in the dark, we have finally cracked the piñata of OCD genetics. This study required unprecedented international collaboration, and I am proud of Sweden's contribution to this effort," said David Mataix-Cols, a world-renowned OCD expert, international collaborator on the study, and professor at the Karolinska Institute in Stockholm.  

Paving way for future OCD research

Estimated to affect more than 400,000 Canadians, OCD causes intrusive thoughts (obsessions) and urges to repeat specific behaviours (compulsions) — symptoms that can be debilitating. Ìý

The more than 200 investigators from dozens of institutes around the world were also able to estimate that around 11,500 different genetic variants likely contribute to OCD risk, with each having a very small effect. Ìý

Dr. Mattheisen explains that the genetic risk factors identified by the team seem to be most active in specific types of brain cells, particularly in excitatory neurons, or nerve cells that stimulate activity, in brain areas that respond to the chemical messenger dopamine. This supports existing theories about which brain circuits might be involved in OCD.   Ìý

Importantly, the study confirmed strong genetic links between OCD and other mental health conditions, like anxiety disorders, depression, anorexia nervosa, Tourette syndrome and PTSD. It also found that the genetic factors linked to higher OCD risk were, however, associated with a lower genetic risk for inflammatory bowel diseases, higher educational attainment, higher body mass index and alcohol dependence.  

"Understanding the shared genetic architecture between OCD and other psychiatric conditions underscores the importance of considering comorbidity in both research and treatment planning," says Dr. Sandra Meier, Canada Research Chair in Developmental Psychopathology and Youth Mental Health at Dal. "This work not only provides insight into the biological roots of OCD but also opens the door to identifying transdiagnostic pathways that may inform more personalized and effective interventions."

The work paves the way for additional OCD research.

"Future studies will require ancestrally diverse samples to facilitate the discovery of additional OCD risk variants, understanding that these results may be useful for drug repurposing and yield new, more effective treatments," concludes Dr. Mattheisen of the faculties of Medicine and Computer Science at 9 1Ãâ·Ñ°æÏÂ. 

Now read
Ìý

• DalSolutions: Putting mental health in reach for low‑income Nova Scotians
  
  
• Dal researchers receive $7.5M for projects to improve mental health and addictions care for youth