Inference-Based Cognitive Therapy Versus Exposure and Response Prevention for Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a highly disabling psychiatric illness, characterized by obsessional thoughts that cause patients to perform time-consuming and distressing compulsive rituals. Exposure and Response Prevention (ERP) is a first-line psychological treatment of choice, which requires patients to face their fears by being exposed to feared stimuli. ERP has been shown to reduce symptoms among those who comply with treatment. However, there is still a significant portion of patients that do not improve, especially those who firmly believe their obsessions are realistic and reasonable (i.e. OCD with Overvalued Ideation (OVI)). Also, a signficant proportion of patients refuse the treatment or drop out during treatment due to the distress provoked by ERP. Even among those that do improve, residual symptoms often remain, or symptoms may reappear after treatment. One evidence-based approach to the treatment of OCD, termed inference-based cognitive therapy (IBCT) has been shown to be as effective as ERP with the potential to overcome some of the limitations of ERP. Since IBCT is a cognitive approach, the treatment does not require exposure to feared stimuli and likely more tolerable for patients with OCD. Also, there is evidence that IBCT is more effective than ERP for those with overvalued ideation, since it directly targets the distorted reasoning that is responsible for the intensity and persistence of the obsession. The current study aims to directly compare ERP with this promising evidence-based cognitive therapy, which is expected to be significantly more effective for those with overvalued ideation, as well as significantly more tolerable with lower rates of treatment refusal, drop-out and higher treatment satisfaction. The project is designed to maximize potential beneficial health outcomes and offer a new evidence-based treatment option for the large proportion of patients unable to benefit from ERP.

The proposed study is a parallel-group randomized controlled trial developed in accordance with CONSORT quality guidelines.The RCT will compare the outcome of 16 sessions of IBCT compared to 16 sessions of ERP in OCD patients. The principal investigators and independent evaluators will be blind to the random allocation treatment conditions with a randomization ratio of 1:1. Both treatments will be administered by trained therapists on a weekly one-on-one basis over a 16-week period with 6-month follow-up conforming to current thinking on relapse in OCD. Conditions of treatment delivery, duration and monitoring will be equivalent across all groups. Both treatments are manualized and any newly engaged therapists will receive intensive training in one therapy protocol to ensure optimal delivery of each modality.

The objective of the present study is to establish IBCT as a psychological treatment that is as effective as ERP, but significantly more tolerable and generalizable for the high proportion of patients who are unable to benefit from ERP.

The hypotheses are that 1) IBCT is non-inferior to ERP; 2) IBCT is superior to ERP among OCD patients with higher levels of OVI; 3) IBCT has lower rates of treatment refusal and drop-out than ERP; and, 4) IBCT has higher levels of acceptability, tolerability, credibility and satisfaction than ERP.

Eligibility Criteria:
Inclusion Criteria:

* a primary diagnosis of OCD according to Diagnostical and Statistical Manual, version 5 criteria;
* no change in medication during the 12 weeks before treatment for antidepressants (4 weeks for anxiolytics);
* willingness to keep medication stable while participating in the study;
* no evidence of suicidal intent;
* no evidence of current substance abuse;
* no evidence of current or past schizophrenia, bipolar disorder or organic mental disorder;
* not undergoing a current psychological treatment;
* willingness to undergo active psychological treatment;
* willingness to undergo randomization into treatment modality;
* fluency in English and French.

Exclusion criteria:

* another primary diagnosis than OCD requiring treatment;
* medication not stabilized for 12 weeks;
* medication will change during the participation;
* suicidal intent.