obsessive-compulsive disorders

**Definition (DSM-5-TR):** OCD is in its own chapter, "Obsessive-Compulsive and Related Disorders." Obsessions are recurrent, intrusive, unwanted thoughts, urges, or images that cause marked anxiety. Compulsions are repetitive behaviors (washing, checking, ordering) or mental acts (counting, praying) that the person feels driven to perform in response to an obsession or by rigid rules. Symptoms take >1 hr/day or cause clinically significant distress or impairment. Insight is specified as good/fair, poor, or absent/delusional. A tic-related specifier also exists.

**Key feature:** Symptoms are ego-dystonic, meaning the patient recognizes them as distressing and excessive. This distinguishes OCD from obsessive-compulsive personality disorder (OCPD), which is ego-syntonic. Patients with OCPD see their perfectionism, rigidity, and orderliness as correct. They lack true obsessions and compulsions.

**Common themes:** - Contamination, which leads to washing - Doubt about harm (e.g., stove left on), which leads to checking - Symmetry or order - Taboo or unacceptable thoughts (aggressive, sexual, religious)

**Epidemiology:** Lifetime prevalence is about 2%. Onset is typically in late adolescence or early adulthood, and there is a bimodal pattern with a second peak in childhood. Males tend to have earlier onset. There is strong comorbidity with depression, anxiety disorders, tic disorders (Tourette), and ADHD.

**Pathophysiology:** - Dysfunction of cortico-striato-thalamo-cortical (CSTC) circuits, including the orbitofrontal cortex, anterior cingulate cortex, and caudate nucleus - Serotonin dysregulation (supported by SSRI response), with glutamate also implicated - Genetic contribution (higher concordance in first-degree relatives) - **PANDAS/PANS:** abrupt pediatric-onset OCD or tics after group A streptococcal infection, thought to involve autoimmune molecular mimicry affecting the basal ganglia

**Treatment:** - **CBT with exposure and response prevention (ERP)** is first-line psychotherapy. - **SSRIs** (fluoxetine, fluvoxamine, sertraline, paroxetine) are first-line pharmacotherapy. They need higher doses and longer trials (8-12 weeks) than for depression. - **Clomipramine** (a TCA with strong serotonin reuptake inhibition) is an effective second-line option. - Augmentation with low-dose antipsychotics (e.g., risperidone, aripiprazole) is used in refractory cases, especially with tics. - Severe refractory cases may be treated with deep brain stimulation, TMS, or cingulotomy.

**Related disorders (DSM-5 OC-spectrum):** - Body dysmorphic disorder - Hoarding disorder - Trichotillomania (hair-pulling) - Excoriation (skin-picking) disorder

**Board pearls:** - Ego-dystonic = OCD, ego-syntonic = OCPD. - Do not confuse obsessions with psychotic delusions. Insight is usually preserved in OCD. - Do not confuse obsessions with the worries of generalized anxiety disorder, which concern real-life problems. - Defense mechanisms in OCD: isolation of affect, undoing, reaction formation, intellectualization. - Sudden-onset OCD in a child after a strep infection suggests PANDAS. - Of the SSRIs, fluvoxamine is used specifically for OCD in some contexts. Clomipramine is the classic TCA answer.