W02 – Co-Occurring Autism Spectrum and Obsessive–Compulsive Disorder: A Review and Synthesis of Diagnosis, Treatment, and Clinical Considerations

W02 – Co-Occurring Autism Spectrum and Obsessive–Compulsive Disorder: A Review and Synthesis of Diagnosis, Treatment, and Clinical Considerations

Thursday, Oct. 27
10:45 – 11:45 (1 hr)
Meeting Room: Maple (Mezzanine)
Peggy Richter*, MD, FRCPC; Pushpal Desarkar*, MD FRCPC; Rahat Hossain, MD; Natasha Fernandes, MD FRCPC; Alex Porthukaran, MA

CanMEDS Roles:

  1. Medical Expert
  2. Scholar
  3. Health Advocate

At the end of this session, participants will be able to: 1) Develop a detailed knowledge of the assessment and treatment for autism spectrum disorder (ASD) and obsessive–compulsive disorder (OCD); 2) Learn to navigate challenges in the diagnosis and misdiagnosis of co-occurring ASD and OCD; and 3) Understand principles for adapting psychotherapy and pharmacotherapy for the treatment of OCD in patients with autism.

Co-occurring obsessive–compulsive disorder (OCD) in people with autism spectrum disorder (ASD) requires specialized assessment and management, given evidence of poorer insight, greater functional impairment, increased symptom severity, and reduced efficacy of treatment. This workshop will help participants better understand and learn to manage these co-occurring conditions. OCD and ASD can be differentiated on the basis of distinguishing between their respective repetitive behaviours; in OCD they are egodystonic and resisted and in ASD they are egosyntonic and pleasurable. Even so, there is limited understanding of the function and mental state behind OCD repetitive behaviours in ASD, because obsessions are uncommon in ASD and there are altered and ambiguous presentations of OCD in those with ASD. The Obsessive-Compulsive Inventory-Revised (OCI-R) is a brief self-reported measure that has been validated for use in verbal adults to help differentiate between ASD and OCD. Treatment with pharmacotherapy remains under-investigated with only fluoxetine showing promise for OCD in children and youth with ASD. Treatment with standard CBT programs for OCD have reduced efficacy in people with OCD and ASD. However, adapted CBT programs for ASD and OCD can result in large effect sizes and gains may persist for up to 11 years. Some adaptations to CBT for OCD in people with ASD include focusing on ERP rather than cognitive elements, using the individuals’ special interests to promote engagement, and presenting information visually rather than verbally. Participants will be equipped with a review of this literature and pearls for their clinical practice.

W02a – Diagnosis of Co-Occurring Obsessive-Compulsive Disorder in Individuals with Autism Spectrum Disorder
Rahat Hossain, MD

At the end of this session, participants will be able to: 1) Learn about the contextual factors underpinning restricted, repetitive behaviours (RRBs) in autism spectrum disorder (ASD) and compulsions in obsessive–compulsive disorder (OCD), respectively, and how to better delineate the role of anxiety; 2) Develop a clinical approach for distinguishing between RRBs and obsessive–compulsive symptoms in patients with ASD of varying insight; and 3) Understand the psychometric properties and application of the Obsessive–Compulsive Inventory-Revised for the screening of OCD in patients with ASD.

Many people with autism spectrum disorder (ASD) also experience symptoms of obsessive–compulsive disorder (OCD), which occur independently of the restricted, repetitive behaviours (RRBs) that can be characteristic of ASD. Though phenomenologically similar, clinicians should assess patients with ASD for obsessions and compulsions that can cause distress and impair functioning and quality of life. Symptoms of OCD in ASD appear similar to those of patients who do not have ASD. However, people with ASD can have difficulty describing their internal states, and there may be impairments in self-awareness and insight. Clinical assessment can yield important differences to detect co-occurring OCD in those with ASD, including the observations that people with both disorders have significantly higher levels of 1) checking, ordering, and obsessional symptoms, compared to the absence of a co-occurring OCD; and 2) ordering and hoarding, compared to those with OCD and no ASD. The Obsessive–Compulsive Inventory-Revised (OCI-R) can be used as a reliable self-reported tool for screening OCD in patients with ASD. A cut-off OCI-R total score of 29 can correctly classify 69% of patients with co-occurring OCD and ASD. This performance corresponds accurately to clinician diagnosis, with a higher cut-off score reflecting the higher levels of repetitive behaviours in ASD compared to other populations. Distinguishing between RRBs and OCD requires assessing the context of the behaviour and using language specific to the behaviour, such as describing repetitive motor movements, insistence on sameness behaviours, and restricted interests for RRBs and labelling the symptom dimensions (e.g., “just right” compulsions) for OCD.


  1. Cadman T, Spain D, Johnston P, et al. Obsessive-compulsive disorder in adults with high-functioning autism spectrum disorder: what does self-report with the OCI-R tell us? Autism Res 2015;8:477–85.
  2. Russell AJ, Mataix-Cols D, Anson M, et al. Obsessions and compulsions in Asperger’s syndrome and high-functioning autism. Br J Psychiatry 2005;186:525–8.

W02b – The Assessment and Diagnosis of Obsessive–Compulsive Disorder
Peggy Richter, MD, FRCPC

At the end of this session, participants will be able to: 1) Discuss the full range of symptoms associated with obsessive–compulsive disorder (OCD); 2) Elicit less common features of OCD that often go unrecognized; and 3) Distinguish between OCD compulsions and restricted repetitive behaviours with greater comfort.

The core symptoms of obsessive–compulsive disorder (OCD) are generally familiar to all; however, OCD has the potential to present in highly heterogeneous ways, which can make the diagnosis unclear. When evaluating people with potential comorbidity with autistic traits or autism spectrum disorder (ASD), this problem can be further compounded. Moreover, OCD itself can impact on speech patterns and fluency, adding to the challenge. In this talk, differing presentations of OCD will be introduced. Specific questions and techniques to assist in eliciting less-recognized symptoms will be shared, as a more comprehensive assessment of clinical features of OCD may aid in the assessment and diagnosis of complex presentations.


  1. Bedford SA, Hunsche MC, Kerns CM. Co-occurrence, assessment and treatment of obsessive–compulsive disorder in children and adults with autism spectrum disorder. Curr Psychiatry Rep 2020;22(10):53.
  2. Paula-Pérez I. Differential diagnosis between obsessive–compulsive disorder and restrictive and repetitive behavioural patterns, activities and interests in autism spectrum disorders. Rev Psiquiatr Salud Ment 2013;6:178–86.

W02c – Pharmacological Considerations for the Treatment of Repetitive and Compulsive Behaviours in Autism Spectrum Disorder
Natasha Fernandes, MD, FRCPC

At the end of this session, participants will be able to: 1) Understand the pharmacologic management of obsessive–compulsive disorder (OCD) in autism spectrum disorder (ASD); 2) Understand the pharmacologic management of restricted repetitive behaviours in ASD; and 3) Appreciate the limitations of the research on this topic.

There is a lack of evidence focused specifically on the pharmacologic management of obsessive–compulsive disorder (OCD) in autism spectrum disorder (ASD). Existing pharmacologic trials often do not distinguish obsessive–compulsive behaviours as being secondary to OCD versus restricted repetitive behaviours (RRBs). When managing OCD in ASD, the National Institute of Health and Care Excellence suggests using their OCD guidelines designed for the general population. No medications are FDA approved for the management of RRBs. Meta-analyses of these studies show no significant difference between medication and placebo. Medications reviewed include fluoxetine, fluvoxamine, risperidone, olanzapine, NAC, buspirone, citalopram, divalproex, levetiracetam, and oxytocin. However, these meta-analyses are limited by a high degree of heterogeneity among studies. Individual fluoxetine, fluvoxamine, and risperidone trials have been shown to have a positive effect specifically in autistic adults with repetitive behaviours. There may be a role for these medications if managing comorbid anxiety that can worsen RRBs. Special consideration should be made for the activating side effects of these medications in ASD. People with autism are susceptible to increased agitation and insomnia with serotonergic agents. Clomipramine in particular has been shown to be poorly tolerated. In one study involving clomipramine, the drop-out rate because of side effects was close to 70%. Starting at low doses and cautiously increasing slowly is advised.


  1. Yu Y, Chaulagain A, Pedersen S, et al. Pharmacotherapy of restricted/repetitive behavior in autism spectrum disorder: a systematic review and meta-analysis. BMC Psychiatry 2020;20:121.
  2. Williams K, Brignell A, Randall M, et al. Selective serotonin reuptake inhibitors (SSRIs) for autism spectrum disorders (ASD). Cochrane Database Syst Rev 2013;(8):CD004677.

W02d – The Phenomenology of Restricted and Repetitive Patterns of Behaviours and Interests in Autism Spectrum Disorder
Pushpal Desarkar, MD, FRCPC

At the end of this session, participants will be able to: 1) Describe the presentation of restricted and repetitive patterns of behaviours (RRBs) and interests in autism spectrum disorder (ASD); 2) List the potential effect of developmental maturation and intellectual ability on the expression of RRBs; and 3) Identify gender-specific expressions of RRBs in ASD.

The restricted and repetitive behaviours (RRBs) in autism spectrum disorder (ASD) include a wide range of behaviours that tend to form three independent clusters: the ‘lower-order’ repetitive motor movements (RMVs) domain, the ‘higher-order’ insistence on sameness (IS) domain, and the circumscribed interest (CI) domain. No single RRB is considered unique to ASD. RRBs are seen in typically developing children, but children with ASD display more frequent RRBs and spend more time engaging in RRBs than children with intellectual disability or typically developing children. RRBs are also present in other neurodevelopmental, genetic, and psychiatric conditions; however, IS and CIs are more frequently seen in ASD, compared to other psychiatric conditions. Although RRBs clearly persist into adulthood, RMVs are related to younger age and lower intellectual ability. By contrast, some studies found an association between IS and CI with older age (i.e., adulthood) and higher intellectual ability. IS has been shown to have association with anxiety. There is a need to recognize how gender modifies the presentation of RRBs in ASD. The previous suggestion that females with ASD could present with less frequent RRBs has been questioned. The ASD phenotype in females can be qualitatively different. For example, while males with ASD tend to focus more on mechanical topics, females with ASD could take special interest in relational purpose, psychology, and fictional characters, etcetera, all of which could look ‘typical’ to a clinician on the surface.


  1. Uljarević M, Jo B, Frazier TW, et al. Using the big data approach to clarify the structure of restricted and repetitive behaviors across the most commonly used autism spectrum disorder measures. Mol Autism 2021;12(1):39.
  2. Hull L, Petrides KV, Mandy W. The female autism phenotype and camouflaging: a narrative review. J Autism Dev Disord 2020;7:306–17.

W02e – Co-Occurring Autism Spectrum Disorder and Obsessive–Compulsive Disorder: Psychological and Psychotherapeutic Considerations
Alex Porthukaran, MA

At the end of this session, participants will be able to: 1) Develop an understanding of the current state of research in the psychotherapeutic treatment of obsessive–compulsive disorder (OCD) in autism; 2) Learn about current cognitive–behavioural therapy (CBT) strategies and techniques that have the potential to be effective with this population; and 3) Highlight the gaps in the research literature and identify theoretical next steps.

People with obsessive–compulsive disorder (OCD) who also are autistic often require modifications to psychological treatment to be successful. According to the National Institute of Health and Care Excellence (NICE) guidelines, treatment for autism should focus on co-occurring mental health conditions, including treatment for OCD. However, there is some evidence that cognitive-behavioural therapy (CBT) without modifications often leads to challenges in implementation with autistic people. There is limited evidence in the types of modifications that are most effective, with some of the evidence in the form of case studies. We will begin our consideration of treatment modifications that have been identified as having some evidence for effectiveness. Given the limitations of the current evidence, theoretical considerations will also be explored. Some of the case studies and a randomized controlled trial will be reviewed. The adaptations outlined in these studies include a shift in focus (e.g., to behavioural aspects of therapy) as well as additional tools in therapy (e.g., integration of social stories and reward systems). The specifics of the adaptations and when they would be effective will be discussed (e.g., children vs. adults, cognitive ability, etc.), and examples of potential adaptations will be shown. Studies also highlight the importance of family factors in treatment outcome. Differentiating between repetitive behaviours and compulsive behaviours at the onset of treatment appears to be crucial. Participants will learn about the key strategies based on the current literature to implement in psychotherapeutic intervention with people with these diagnoses.


  1. Elliott SJ, Marshall D, Morley K, et al. Behavioural and cognitive behavioural therapy for obsessive compulsive disorder (OCD) in individuals with autism spectrum disorder (ASD). Cochrane Database Syst Rev 2021;9(9):CD013173.
  2. Russell JA, Fullana MA, Mack H, et al. Cognitive behavior therapy for combined obsessive-compulsive disorder in high-functioning autism spectrum disorders: a randomized control trial. Depress Anxiety 2013;30:697–708. https://doi.org/10.1002/da.22053.