Background: Cognitive behavioural therapy (CBT) is a successful treatment of obsessive compulsive disorder (OCD). It is known to induce changes in cerebral metabolism; however, the dynamics of these changes and their relation to clinical change remain largely unknown, precluding the identification of individualized response biomarkers.
Method: In order to study the dynamics of treatment response, we performed systematic clinical and functional magnetic resonance imaging (fMRI) evaluation of 35 OCD patients immediately before a 3-month course of CBT, halfway through and at its end, as well as 6 months after. To sensitize fMRI probing, we used an original exposure task using neutral, generic and personalized obsession-inducing images.
Results: As expected, CBT produced a significant improvement in OCD. This improvement was continuous over the course of the therapy; therefore, outcome could be predicted by response at mid-therapy (r 2 = 0.67, p < 0.001). Haemodynamic response to the task was located in the anterior cingulate and orbitofrontal cortices and was stronger during exposure to personalized obsession-inducing images. In addition, both the anxiety ratings and the haemodynamic response to the obsession-inducing images in the anterior cingulate and the left but not the right orbitofrontal clusters decreased with symptom improvement. Interestingly, haemodynamic activity continued to decrease after stabilization of clinical symptoms.
Conclusions: Using an innovative and highly sensitive exposure paradigm in fMRI, we showed that clinical and haemodynamic phenotypes have similar time courses during CBT. Our results, which suggest that the initial CBT sessions are crucial, prompt us to investigate the anatomo-functional modifications underlying the very first weeks of the therapy.