Extended formulation in cognitive behavioural therapy for OCD: A single case experimental design

Eleanor Chatburn, Josie Millar, Joachim Ryan

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The demanding nature of exposure work that forms an essential component of exposure and response prevention (ERP) for obsessive compulsive disorder (OCD) is for some patients intolerable and leads to disengagement. The addition of cognitive therapy to ERP (CBT) with a focus on developing a shared understanding of how OCD works may aid engagement. This paper reports a case study of an individual who had not responded to two previous courses of ERP due to engagement difficulties with the treatment rationale. This study aimed to establish if CBT for OCD, incorporating an extended period of assessment and longitudinal formulation, would: (1) aid in engagement with the treatment rationale and therapy and (2) lead to an improvement in OCD symptoms, general functioning and mood. An A-B single case experimental design was used. Standardised measures were collected at weekly intervals over 15 sessions of CBT, in conjunction with pre-post idiographic behavioural measures. The extended formulation was successful in helping the individual to develop a less threatening understanding of how OCD works, enabling her to engage in therapy. This led to a reduction in the duration of the overt compulsions in her behavioural measures although on the standardised measures there was no change in self-reported OCD symptoms. The patient's covert rituals and underlying responsibility and control beliefs largely remained intact, thus maintaining her OCD and requiring further intervention. There was a significant improvement in social functioning and consequently the patient reported being able to regain a sense of some control in her life.Key learning aims(1)To describe the factors that might lead to a patient disengaging from exposure work in treatment for OCD.(2)To identify the advantages and disadvantages of incorporating a period of extended formulation when working with patients who have not previously been able to tolerate exposure work.(3)To describe ways of monitoring observable improvements in areas of functioning that matter to the patient in order to help them to celebrate their progress and boost their sense of self-efficacy.

Original languageEnglish
Article numbere38
JournalCognitive Behaviour Therapist
Early online date25 Sep 2020
Publication statusPublished - 2020


  • case formulation
  • CBT
  • cognitive behavioural therapy
  • ERP
  • exposure and response prevention
  • obsessive compulsive disorder
  • OCD

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