Cognitive behavioural therapy with exposure and response prevention has long been the standard psychological treatment for obsessive compulsive disorder. It involves gradually facing the situations that set off obsessions while resisting the compulsions that usually follow. Acceptance and commitment therapy, or ACT, takes a different route, teaching people to make room for distressing thoughts and urges while still acting on what matters to them. The target is the response, not the thought. Until now the two had never been compared directly in a randomised trial.
Nielsen and colleagues randomly assigned 176 adults with OCD attending two outpatient clinics to 14 weekly sessions of either group ACT or group CBT with exposure and response prevention. Symptoms were rated on the Yale-Brown Obsessive Compulsive Scale, the standard measure used in OCD research. ACT proved non-inferior. That is, it did not perform worse than the established treatment, either at the end of the 14 weeks or at the 6-month and 12-month follow-ups, and quality of life scores showed no significant difference between the groups.
The authors are careful to say the finding needs replication before too much is read into it. Even so, it points to more than one workable path through OCD, which matters for anyone who has found exposure work difficult to begin.
If OCD is taking up your time or narrowing your life, support is available.
What the two treatments involve
Exposure and response prevention sits inside cognitive behavioural therapy and is the most established psychological treatment for OCD. A person works through feared situations in a planned, graded way while deliberately not performing the compulsion that would normally bring relief. Over time the anxiety attached to the trigger settles, and the belief that the compulsion is necessary weakens.
Acceptance and commitment therapy works from a different premise. Rather than targeting the content of obsessions, it builds a person's willingness to have unwanted thoughts and sensations present without acting on them, while committing to behaviour tied to their own values. Both approaches ask people to stop doing compulsions. They differ in what they treat as the mechanism of change.
What the study did
The researchers ran a single-blinded, non-inferiority, block randomised controlled trial across two outpatient mental health clinics. Non-inferiority is worth pausing on. A conventional trial asks whether one treatment beats another. A non-inferiority trial asks a narrower question: whether the new treatment stays within an acceptable margin of the established one, set in advance. It is the right design when an alternative is being tested not because it might be better, but because it might be a genuine option alongside what already works.
A total of 176 adults with OCD took part, with 101 assigned to group ACT and 75 to group CBT with exposure and response prevention. Both groups received 14 weekly sessions. The main outcome was the Yale-Brown Obsessive Compulsive Scale, the standard clinician-rated measure of OCD severity, assessed after treatment and at follow-up. Quality of life, measured with the Quality of Life Inventory, was the secondary outcome. Single-blinding here means the assessors rating symptoms did not know which treatment a participant had received, which guards against expectations shaping the scores.
What it found
Using linear mixed models, a statistical method suited to repeated measurements of the same people over time, the ACT group's Yale-Brown scores were non-inferior to the CBT group's immediately after treatment and again at 6 and 12 months. Quality of life scores showed no significant difference between the groups at any of the three measurement points.
Nothing in these results says ACT is superior. The claim being tested, and supported, is that group ACT did not fall short of the established treatment by more than the pre-specified margin, and that this held up over a year rather than only at the end of sessions.
Why it matters, and what it does not settle
Exposure and response prevention is effective, but it asks a great deal of a person early on, and some people decline it or stop. A second approach with comparable results widens what can be offered, particularly in a group format where clinician time reaches more people.
Two cautions belong with this. The trial was conducted in outpatient mental health clinics with adults, so it speaks to that setting rather than to every presentation of OCD. The authors themselves state that further replication is necessary, and a single non-inferiority trial is a reason to take an alternative seriously, not to reorganise practice around it.
If obsessions and compulsions are shaping your days, a psychologist can talk you through the options and help you decide where to start.