OCD

DEFINITION / DSM-5: OCD (classified under "Obsessive-Compulsive and Related Disorders") requires obsessions and/or compulsions that are time-consuming (>1 hr/day) or cause significant distress/impairment, not attributable to a substance or another medical condition. Specifiers: good/fair insight, poor insight, absent insight/delusional beliefs; tic-related.

KEY FEATURES: - Obsessions: recurrent, intrusive, unwanted thoughts/urges/images causing anxiety (contamination, symmetry/order, aggression, taboo sexual/religious thoughts, doubt/harm). Ego-dystonic: the patient recognizes them as excessive/irrational and is distressed by them. Contrast with OCPD, which is ego-syntonic. - Compulsions: repetitive behaviors (washing, checking, counting, ordering) or mental acts (praying, counting silently) done in response to an obsession or by rigid rules to reduce anxiety. They are not pleasurable. - Reality testing is intact (unlike psychosis), although some patients have poor insight.

EPIDEMIOLOGY: Lifetime prevalence is about 2-3%. Bimodal onset: childhood (males more often, often with tics) and late adolescence/early adulthood. Overall, men and women are affected about equally. Comorbid with depression, anxiety disorders, tic disorders/Tourette, ADHD, and other OC-spectrum disorders (body dysmorphic disorder, trichotillomania, hoarding, excoriation disorder).

PATHOPHYSIOLOGY: Dysfunction of cortico-striato-thalamo-cortical (CSTC) circuits, involving orbitofrontal cortex, anterior cingulate cortex, and caudate (striatal hyperactivity). Serotonin dysregulation is implicated (SSRIs are effective). Glutamate and dopamine are also involved. There is a genetic component (higher concordance in twins and first-degree relatives).

PANDAS/PANS: Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections. Abrupt-onset OCD/tics after group A strep infection, thought to arise from molecular mimicry with antibodies against basal ganglia.

TREATMENT: - First line: SSRIs (fluoxetine, fluvoxamine, sertraline, paroxetine, etc.), usually at higher doses and for longer trials (8-12 weeks) than for depression, and/or CBT with exposure and response prevention (ERP). Combination therapy is often used for moderate-severe disease. - Clomipramine (a TCA with strong serotonin reuptake inhibition) is effective, but it is second line because of its side effects (anticholinergic effects, sedation, weight gain, seizure risk, QT prolongation, serotonin syndrome risk). - Augmentation for refractory cases: low-dose antipsychotics (e.g., risperidone, aripiprazole), especially with comorbid tics. - Severe refractory cases: deep brain stimulation, TMS, or (rarely) cingulotomy.

DIFFERENTIAL (high-yield): - OCPD: ego-syntonic, preoccupied with perfectionism, orderliness, and control, with no true obsessions or compulsions. - Generalized anxiety disorder: worries about real-life concerns, with no compulsions. - Illness anxiety disorder: fixation on having a serious illness. - Body dysmorphic disorder: preoccupation with a perceived physical flaw. - Tourette/tic disorders: tics are not driven by obsessions, though they commonly co-occur with OCD. - Schizophrenia: delusions are ego-syntonic and reality testing is impaired. - Autism spectrum disorder: restricted, repetitive behaviors.

BOARD PEARLS: - Ego-dystonic = OCD; ego-syntonic = OCPD. - The compulsion is performed to relieve the anxiety from the obsession. - The defense mechanisms classically associated with OCD are isolation of affect, undoing, and reaction formation. - Treatment: SSRI + ERP; clomipramine is the classic TCA answer. - Child with sudden-onset OCD after strep pharyngitis: think PANDAS.