Diagnosis and treatment of obsessive–compulsive disorder

Establishing diagnosis

As in other psychiatric disorders, the diagnosis is established through detailed clinical evaluation. Structured diagnostic interview schedules such as Structured Clinical Interview for Diagnostic and Statistical Manual 5th edition (DSM-5) (SCID-5 Clinician or Research version)¹² and diagnostic interview for Anxiety, Mood and Obsessive Compulsive and related disorders (DIAMOND) are available for both adults¹³ and children.¹⁴ They are time-consuming and not practical to administer in routine clinical settings. A clinical history is often adequate for diagnosis in the majority of cases. The International Classification of Diseases 11th edition and the DSM-5 provide explicit diagnostic criteria for diagnosing all psychiatric disorders, including OCD (Table I).

The obsessive thoughts and compulsive actions are often centred around a few common themes (Table II). Although patients can present with more than one theme, it is generally consistent throughout the illness. There are specific scales, such as the Dimensional Obsessive–Compulsive Scale and Yale– Brown Obsessive–Compulsive Scale (Y-BOCS) checklist for adults and children, which can be used to assess various types of obsessions and compulsions.

Other important terminologies in the context of OCD are:

1. Avoidance: It is a common behaviour where a person engages in avoiding triggers to reduce negative outcomes based on their fears (Table II).¹⁵

2. Mental compulsions: Compulsions can occur as voluntary mental acts (as opposed to physical behaviours) in some patients, e.g. mental reviewing, checking, self-reassurance, etc., which can be equally distressing and time-consuming.¹⁶

Comorbid conditions

A meta-analysis found psychiatric co-morbid conditions in 69% of patients of a pooled sample of OCD patients.¹⁷ The most common are mood disorders, followed by anxiety disorders.¹⁷

Mood disorders: Depressive disorders are more common but bipolar disorder also occurs at increased rates compared to the general population.

Anxiety disorders: Panic disorder, generalized anxiety disorder and social anxiety disorder are common.

Other obsessive–compulsive-related disorders: Body dysmorphic disorder, body-focussed repetitive behaviours, hoarding and hypochondriasis can co-exist.

Psychotic disorders: OCD symptoms can occur in patients with schizophrenia or sometimes as an adverse effect of specific antipsychotic medications (e.g. clozapine).

Neurodevelopmental conditions: Attention–deficit hyperactivity disorder, autism spectrum disorder and tic disorders are commonly seen in childhood-onset OCD.

Others: Personality disorders, substance use disorder, etc. are known to co-occur commonly in OCD increasing both treatment complexities and morbidity of illness.

Suicide: Studies report the suicide attempt rate to be between 12% and 27%.¹⁸ Hence, it is always important to look for the risk of suicide in any patient diagnosed with OCD.

Neurological disorders: OCD is also described in neurological disorders involving basal ganglia dysfunction such as Huntington’s disease, Sydenham chorea, dementia and ischaemic stroke.

Differential diagnosis

1. Anxious preoccupations in generalized anxiety disorder and depressive rumination in depression might resemble obsessions. However, a patient does not recognize these thoughts as excessive/irrational, and they are not associated with compulsive rituals.¹⁹

2. A person with an obsessive–compulsive personality disorder may be meticulous in day-to-day activities and have preoccupations about orderliness. These are often not associated with repetitive behaviours and may not be considered irrational.¹⁹

3. Poor insight in OCD may need to be differentiated from delusions in schizophrenia. Accompanying compulsions to reduce anxiety associated with obsessions suggest a diagnosis of OCD, while the presence of hallucinations, affective blunting and other psychotic symptoms suggests a diagnosis of psychosis.²⁰

The Y-BOCS scale for adults and children is the gold standard for assessing the severity of OCD.²¹

Psychoeducation

It forms an important component of treatment. Emphasizing that their symptoms are a manifestation of a disorder with a label often reassures the patient and decreases stigma. The link between obsessions and compulsions, the course and treatment strategies available and the need for long-term follow-up have to be discussed.²²

Pharmacological treatment

Selective serotonin reuptake inhibitors (SSRIs) are the first- line treatment for OCD and have shown consistent efficacy and better tolerability in multiple randomized controlled trials and meta-analyses.^2,22 No SSRI is found to be superior over others in terms of efficacy. Hence, factors such as cost, adverse effects and previous response are to be considered while choosing between SSRIs (Table III).^23–29 Guidelines recommend upward titration to maximum tolerable doses within 4–6 weeks and further continuation for 6–8 weeks for an adequate trial.²²

The adverse effects include gastrointestinal disturbances, sexual dysfunction, weight gain, drug interactions and hyponatraemia, which are common amongst all SSRIs. Serotonin syndrome is a rare complication due to overactivation of both central and peripheral serotonergic receptors and can cause a range of severity between triads of altered sensorium, autonomic hyperactivity and neuromuscular abnormalities (rigidity and myoclonus). Hence, caution must be exercised while titrating doses and cross-tapering. Individual differences in side-effects amongst SSRIs and propensity for side-effects/drug interactions pertinent to specific population groups are discussed in Table III. Considering the cost, availability, ease of titration and decreased propensity for drug interactions, escitalopram may be acceptable for many patients.

Around half the patients may respond to their first trial of SSRI. In case of treatment failure, trial of another SSRI can be considered. If there is a partial response to an SSRI, augmentation with cognitive behaviour therapy (CBT), low-dose anti-psychotics (risperidone 2 mg or aripiprazole 10–15 mg) or glutamatergic agents (memantine 20 mg) can be considered. Due to poor tolerability, clomipramine can be considered if there is a poor response to at least 2 SSRIs.

CBT can be provided as a standalone treatment for mild- to-moderate OCD. It can also be used as an augmentation in partial responders/non-responders to medication. Exposure and response prevention is the recommended therapeutic technique. However, this should be provided by a trained therapist. Hence, referral to a psychiatrist/clinical psychologist may be provided if CBT is preferred.

Referral to specialist care

Referral to specialist care may be required in certain situations (Fig 1). Indications for referral include (i) severe illness, (ii) non- responsive to first-line treatments, (iii) need for CBT, and (iv) presence of severe psychiatric comorbid conditions/suicidal thoughts.

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FIG 1.

When to refer a patient with obsessive–compulsive disorder (OCD) for specialist careSSRI selective serotonin reuptake inhibitor

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