Study links DNA methylation to OCD psychotherapy treatment response

OCD is a mental health disorder characterized by unwanted, recurring thoughts and repetitive behaviors that can severely interfere with everyday life. Exposure-based psychotherapy is one of the most effective treatments, but the biological mechanisms underlying treatment response remain poorly understood.

To investigate this, researchers from the University of Bergen studied DNA methylation, an epigenetic mechanism in which small chemical groups attach to DNA and can influence gene activity without changing the genetic code.

The researchers analyzed saliva samples from approximately 900 people with OCD who received an intensive form of exposure-based psychotherapy known as the Bergen 4-Day Treatment at eight clinics across Norway. Samples were collected before treatment, immediately afterward, and at a three-month follow-up.

The study identified several DNA regions where methylation was associated with treatment response. Some differences in DNA methylation were already present before treatment or remained stable over time. Many of these showed strong genetic influences, suggesting that they may reflect relatively stable biological characteristics associated with treatment response. Changes in DNA methylation over time were also associated with treatment outcomes. Unlike the more stable patterns, these changes showed no detectable genetic influences but were also associated with other clinical factors, such as medication use.

The identified DNA methylation differences were located in or near genes involved in biological processes such as brain plasticity, stress responses, immune function, gene regulation, and energy production within cells.

The findings highlight the potential of epigenetic markers to help predict individual responses to psychotherapy, which could eventually contribute to more personalized treatment for OCD. However, the observed associations do not establish causal relationships, and further research is needed to determine whether these markers can reliably predict treatment outcomes in clinical practice.