Chapter 15: Obsessive-Compulsive and Related Disorders

The historical context traces the evolution from early psychodynamic theories to contemporary neurocircuitry models, establishing how understanding of these disorders has fundamentally shifted toward biological and cognitive frameworks. Obsessive-compulsive disorder itself presents with persistent intrusive thoughts paired with compulsive rituals performed to reduce anxiety, manifesting across several symptom dimensions including contamination fears, checking behaviors, symmetry concerns, and forbidden ideation. The chapter emphasizes diagnostic criteria, insight levels, and the important tic-related specifier for cases with concurrent Tourette syndrome. Epidemiological data reveals a lifetime prevalence of 2 to 3 percent, with typical onset in childhood or adolescence, high rates of comorbid depression and anxiety, and substantial suicide risk. The neurobiological foundation centers on dysfunction within cortico-striatal-thalamic-cortical circuits involving serotonergic, dopaminergic, glutamatergic, and GABAergic neurotransmitter systems, supported by neuroimaging, genetic, and cognitive-affective research. Treatment approaches combine pharmacological interventions, with selective serotonin reuptake inhibitors and clomipramine as first-line agents, supplemented by dopamine antagonists or glutamatergic modulators in refractory cases, alongside evidence-based psychotherapies including exposure and response prevention and cognitive-behavioral therapy. The chapter extends beyond obsessive-compulsive disorder to encompass body dysmorphic disorder, characterized by preoccupation with perceived appearance flaws and mirror-checking compulsions, hoarding disorder distinguished by persistent inability to discard possessions despite clutter-related hazards, and body-focused repetitive behavior disorders including trichotillomania and excoriation disorder, each with distinct clinical presentations and treatment considerations. Advanced interventions such as deep brain stimulation and transcranial magnetic stimulation are discussed for treatment-resistant presentations. Throughout, the chapter underscores themes of early onset, chronic course, underdiagnosis, high morbidity, and the necessity of family involvement, cultural competence, and integrated multimodal treatment strategies.