CBT cut OCD symptoms sharply -- and changed a brain signal for holding back

In a randomized trial of 60 adults with OCD, 77.8% of those receiving 12 CBT sessions met response criteria versus 7.7% on the waitlist, and 37% reached remission. The brain's No-Go P3 signal, an electrical marker of inhibition, increased alongside.

Cognitive behavioural therapy with exposure and response prevention is the established psychological treatment for obsessive-compulsive disorder, but what it changes in the brain is unsettled. One candidate is response inhibition, the ability to stop an action before you take it, which is measurably weaker in OCD and maps neatly onto the experience of not being able to resist a compulsion. Researchers led by Metin Cinaroglu randomised 60 adults meeting DSM-5 criteria for OCD to 12 individual CBT sessions or a waitlist, and measured both symptoms and EEG during a Go/No-Go task, in which participants press a button for one cue and must withhold it for another. Fifty-three completed both assessments. The clinical results were decisive: 21 of 27 in the CBT group (77.8%) met the standard response threshold of a 35% Y-BOCS reduction, against 2 of 26 on the waitlist (7.7%), and 10 (37%) reached remission, the group moving from the moderate-to-severe range into the mild range. Obsessive beliefs and intolerance of uncertainty dropped in parallel. The electrophysiology moved as predicted too, with the No-Go P3 -- a brain response around 300 to 600 milliseconds after a stop cue, read as the signature of active inhibition -- increasing in amplitude after treatment. That the symptoms improved is not in doubt; the brain interpretation needs more care. The control was a waitlist, not an active therapy, so expectancy, therapist attention and simple engagement are not controlled for, and repeating the same Go/No-Go task invites practice effects that could produce part of the change. The clinician scoring symptom severity knew who had been treated. The EEG used a 14-channel portable headset, which the authors are careful to say supports scalp-level claims only, not statements about specific brain regions. And with 53 completers from a single cultural setting, no follow-up beyond the end of treatment, and no healthy comparison group, it is unknown whether the signal normalised or merely shifted.