This systematic review included (to 24 August 2020) randomised controlled trials (RCTs), cross-over, cluster- and quasi-randomised controlled trials involving participants of any age, both adults and children with diagnoses of OCD and ASD. Following databases were used: (CENTRAL), MEDLINE, Embase, PsycINFO, five other bibliographic databases, international trial regesteries and other sources of grey literature (to 24 August 2020). Addiotionally, the reference lists of included studies and relevant systematic reviews were checked to identify additional studies missed from the original electronic searches. Moreover, the experts by experience were contacted for further information when needed. Three review authors independently screened studies for inclusion. At least two review authors independently screened titles and abstracts for inclusion. The full-text study reports of potentially eligible studies were retrieved, and at least two review authors independently examined them for compliance with eligibility criteria. The authors extracted relevant data from the eligible studies, assessed the risk of bias and certainty of evidence (GRADE).
Studies of participants with co-occurring conditions (i.e. those experiencing other mental illnesses or neurodevelopmental conditions at the same time) were included, but individuals who had a co-occurring global learning difficulty were not included. Treatment could be in any setting or format and include behavioural therapy (BT) and cognitive behavioural therapy (CBT), which may have been adapted for those with ASD.
Comparator interventions included no treatment, waiting list, attention placebo, and treatment as usual (TAU). TAU could include allocation of a case worker or involvement in groups where supportive counselling or help with problem-solving could be accessed, but where formal CBT was not provided.
Outcomes of interest were changes in OCD symptoms and treatment completion (primary outcome), and severity of depressive symptoms, anxiety symptoms and behavioural difficulties, as well as degree of family accommodation (secondary outcomes).
Only one RCT of 46 participants (recruited from specialist ASD and OCD clinics and generic mental health services with confirmed diagnosis of ASD, verbal intelligence quotient (IQ) greater than 70, co-occurring OCD, no other significant comorbidities and age between 14 and 65 years) was included in this analysis. There were a number of trials of CBT for co‐occurring anxiety disorder and ASD. These trials included people with OCD under the anxiety disorders. However, the numbers of people with OCD remained small in these studies, and the outcomes for people with OCD were not measured separately from the other participants, and for that reason were not included.
The included study compared CBT with ERP for patiens with OCD co-occuring with high-functioning ASD with a control group who received anxiety management only. CBT was predominantly ERP-based and the therapists used ASD adaptations to standard CBT for OCD. Anxiety management provided therapist contact, psychoeducation about anxiety, and general anxiety reduction techniques, but it did not contain any ERP or any cognitive strategies addressing OCD-related beliefs. Up to 20 therapist sessions of approximately one hour per session were allowed in both study arms.
Outcomes relevant to this review were of OCD symptoms using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) total severity rating as a primary outcome and depressive symptoms using the Beck Depression Inventory (BDI), anxiety symptoms using the Beck Anxiety Inventory (BAI), and quality of life using the Work and Social Adjustment Scale (WSAS) as secondary outcomes. Assessors who were blind to treatment group, and who were trained clinicians experienced in administering the Y-BOCS and interviewing people with ASD, rated symptoms at six time points: before treatment (no more than four weeks before the first treatment session), at end of treatment (one week after the final session) and at one-, three-, six- and twelve-month follow-up.
There were no differences in rates of treatment completion between the CBT (87%) and anxiety management (87%) groups (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.80 to 1.25; low-certainty evidence). At the end of treatment, differences using Y-BOCS (MD -3.00, 95% CI -8.02 to 2.02; low-certainty evidence) favoured the CBT group over the control group. However, the 95% CI indicated a high level of imprecision. Also, differences in depression symptoms according to BDI (MD -1.80, 95% CI -11.50 to 7.90), anxiety symptoms according to BAI (MD -3.20, 95% CI -11.38 to 4.98), and quality of life according to WSAS (MD 5.20, 95% CI -1.41 to 11.81), favoured the CBT group, but with a high level of imprecision indicated by the wide 95% CI.
Data from a pilot study indicated that, in order to detect statistically significant differences between groups on the primary outcome measure, 19 participants would be needed for each of the CBT and anxiety management treatment groups, respectively.
This systematic review assessed the effectiveness of behavioural and cognitive behavioural therapy for obsessive compulsive disorder (OCD) in children and adults with autism spectrum disorder (ASD). Only one published randomised controlled trial of delivery of CBT with ERP to people with OCD and ASD met the search criteria. An extensive search of the literature was conducted to minimise the risk of missing relevant studies. The risk of bias and certainty of evidence (GRADE) was assessed. The review indicates that CBT may be an effective treatment for OCD co-occurring with ASD, although evidence is very limited. There is not yet clear evidence that CBT is more effective than anxiety management.