Chapter 16: Psychopathology: Biological Bases

Psychopathology: Biological Bases begins by defining schizophrenia, a severe disorder affecting approximately 1% of the population, characterized by positive symptoms like auditory hallucinations and delusions, and negative symptoms such as emotional withdrawal. The text analyzes the heritability of schizophrenia through twin and adoption studies, highlighting the interaction between genetic susceptibility (such as the DISC1 gene mutation) and environmental stressors like prenatal infections or city living. Significant neurobiological findings are detailed, including enlarged cerebral ventricles, cellular disarray in the hippocampus, and the hypofrontality hypothesis which suggests reduced frontal lobe activity. The summary explains the evolution of pharmacological treatments, from the accidental discovery of chlorpromazine and the subsequent formulation of the dopamine hypothesis, to the glutamate hypothesis derived from the effects of PCP and ketamine, and the development of atypical antipsychotics. The chapter then shifts to mood disorders, distinguishing between bipolar disorder, which involves cycling episodes of mania and depression often treated with lithium, and major depressive disorder (unipolar depression). It delves into the neurochemistry of depression, specifically the monoamine hypothesis involving serotonin and norepinephrine, and the crucial role of the hypothalamic-pituitary-adrenal (HPA) axis, evidenced by abnormal cortisol levels and dexamethasone suppression rates. Sleep architecture changes in depression, such as reduced slow-wave sleep and rapid REM onset, are also covered. The discussion extends to anxiety disorders, including phobias and panic disorder, explaining the efficacy of benzodiazepines in enhancing GABAergic inhibition. Posttraumatic stress disorder (PTSD) is examined through the lens of memory and fear conditioning, noting the association with smaller hippocampal volume and the failure of fear extinction mechanisms. Finally, the chapter addresses obsessive-compulsive disorder (OCD) and Tourette’s syndrome, linking these conditions to abnormalities in the basal ganglia and orbitofrontal cortex, and discussing treatments ranging from SSRIs and cognitive behavioral therapy to neurosurgical interventions like cingulotomy and deep brain stimulation.