Cognitive behaviour therapy (CBT) for OCD developed as an attempt to increase adherence to ERP, by helping the individual to modify dysfunctional thoughts and beliefs (Salkovskis and Warwick, 1985). However, as theoretical and empirical studies on cognitions in OCD developed, CBT has evolved as a treatment in its own right. It is based on modifying key beliefs and appraisals so that the individual learns that intrusive thoughts are not of special significance and do not indicate increased responsibility or probability of harm. CBT aims to help the individual to construct and test a new and less threatening model of their experience through developing an understanding of how the problem may be working and then testing this out through behavioural experiments to learn that the problem is about thinking and worry, rather than actual danger or harm. Whereas in ERP the individual is encouraged to stop carrying out compulsions, in CBT the individual is encouraged to carry out experiments to identify and challenge their misinterpretations. As a result, they learn that they no longer need to carry out compulsions.
It is clear that CBT is effective in significantly reducing symptoms of OCD and that these gains are maintained post-treatment (Clark, 2004). There is evidence that it is effective with symptoms that have been more difficult to treat with ERP, such as obsessional ruminations and hoarding (Freeston et al., 1997; Hartl and Frost, 1999). More recently, controlled trials with adults have compared CBT to ERP and found CBT to be superior to ERP in reducing symptom severity and shifting obsessional beliefs (Rector et al., 2006; Salkovskis et al., in press).
