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Chapter 18 Biopsychology of Psychiatric Disorders The Brain Unhinged This multimedia product and its contents are protected under copyright law. The following are prohibited by law: • any public performance or display, including transmission of any image over a network; • preparation of any derivative work, including the extraction, in whole or in part, of any images; • any rental, lease, or lending of the program. Copyright © 2009 Allyn & Bacon Psychiatric Disorders Also called “psychological disorders” Disorders of psychological function that require treatment by a mental health professional Neuropsychological disorders are a product of dysfunctional brains, but so are psychiatric disorders Historical views: Neuropsychological disorders are brain problems Psychiatric disorders are mind problems Copyright © 2009 Allyn & Bacon Schizophrenia “Splitting of psychic functions” Refers to the breakdown of integration of emotion, thought, and action Affects 1% of the population A diverse disorder – multiple types exist with varied profiles Some symptoms: delusions, hallucinations, odd behavior, incoherent thought, inappropriate affect Only two needed for one month for diagnosis Copyright © 2009 Allyn & Bacon Causal Factors in Schizophrenia Clear genetic basis Inherit an increased risk for the disorder Multiple causes Several different chromosomes implicated Associated with various early insults – infections, autoimmune reactions, toxins, traumatic injury, stress Copyright © 2009 Allyn & Bacon Antipsychotic Drugs Much of our understanding of schizophrenia is a consequence of the drugs that are able to treat it Chlorpromazine – calms many agitated schizophrenics and activates many emotionally blunt schizophrenics Copyright © 2009 Allyn & Bacon Dopamine Theory of Schizophrenia 1960 – link between dopamine and Parkinson’s disease established Antipsychotic drug side effects suggests role for dopamine – drugs work by decreasing dopamine levels; schizophrenia associated with dopamine overactivity Reserpine depletes brain of dopamine and other monoamines by making vesicles leaky Amphetamine and cocaine are dopamine agonists and produce psychosis Copyright © 2009 Allyn & Bacon Dopamine Theory of Schizophrenia (continued) Chlorpromazine antagonizes dopamine activity by binding and blocking dopamine receptors In general, the higher affinity a drug has for dopamine receptors, the more effective it is in treating schizophrenia Haloperidol – an exception. While most antipsychotics bind to D1 and D2 receptors, it and the other butyro-phenones bind to D2 Copyright © 2009 Allyn & Bacon Copyright © 2009 Allyn & Bacon Dopamine Theory of Schizophrenia (continued) Positive correlation between neuroleptic D2 binding and clinical potency Copyright © 2009 Allyn & Bacon Problems with the D2 Theory Clozapine, an atypical and effective neuroleptic, acts at D1, D4, and serotonin receptors, but has only some binding to D2 receptors Neuroleptics act quickly at the synapse, but don’t alleviate symptoms for weeks Schizophrenia associated with brain damage Little damage to dopamine circuitry Damage not explained by dopamine theory Neuroleptics are only effective for some Copyright © 2009 Allyn & Bacon Affective Disorders Depression – normal reaction to loss, abnormal when it persists or has no cause Mania – overconfidence, impulsivity, distract-ibility, and high energy Bipolar affective disorder – depression with periods of mania Unipolar affective disorder – depression only Reactive – triggered by negative event Endogenous – no apparent cause Copyright © 2009 Allyn & Bacon Causal Factors in Affective Disorders (continued) Stressful experiences Evidence linking stress and affective disorders is sparse Extreme stress is more likely to cause posttraumatic stress disorder (PTSD) than depression Seasonal Affective Disorder (SAD) Wintertime depression and lethargy Probably due to reduction of sunlight More common in northern than southern latitudes Light therapy helps Copyright © 2009 Allyn & Bacon Antidepressant Drugs Monoamine oxidase inhibitors (MAOIs) – Iproniazid Prevent breakdown of monoamines Must avoid foods high in tyramine – “cheese effect” Tricyclic antidepressants – Imipramine Block reuptake of serotonin and norepinephrine Safer than MAOIs Copyright © 2009 Allyn & Bacon Antidepressant Drugs (continued) Blocking of serotonin reuptake by fluoxetine (Prozac) Copyright © 2009 Allyn & Bacon Selective Monoamine Reuptake Inhibitors Selective serotonin-reuptake inhibitors (SSRIs), for example Include Prozac, Paxil, Zoloft, and others No more effective than tricyclics, but side effects are few and they are effective at treating other disorders Selective norepinephrine-reuptake inhibitors (SNRIs) are also effective Copyright © 2009 Allyn & Bacon Brain Pathology and Bipolar Affective Disorder Inconclusive evidence for reduction of size of brain or individual components due to bipolar affective disorder (MRI data) Reports of shrinkage of amygdala, striatum, hippocampus, and prefrontal cortex, but Meta-study found no statistically significant evidence for brain shrinkage in bipolar patients Copyright © 2009 Allyn & Bacon Monoamine Theory of Depression Underactivity of serotonin and norepinephrine synapses Consistent with drug effects Depression untreated with drugs may result in proliferation of monoamine receptors (up-regulation), providing support for the monoamine theory Problem with theory – not all respond to monoamine agonists Copyright © 2009 Allyn & Bacon Anxiety Disorders Anxiety – fear in the absence of threat Anxiety disorder – when anxiety interferes with normal functioning Accompanied by physiological symptoms – tachycardia, hypertension, sleep disturbances, nausea, etc. Most prevalent psychiatric disorders Copyright © 2009 Allyn & Bacon Five Classes of Anxiety Disorders Generalized anxiety disorders – stress and anxiety in the absence of a causal stimulus Phobic anxiety disorders – similar to generalized, but triggered by a particular stimulus Panic disorders – attacks of extreme fear and stress; may occur with other disorders or alone Obsessive-compulsive disorders (OCDs) – obsessive thoughts alleviated by compulsive actions Posttraumatic stress disorder – pattern of psychological distress following extreme stress Copyright © 2009 Allyn & Bacon Pharmacological Treatment of Anxiety Disorders Benzodiazepines (Librium, Valium) Also used as hypnotics, anticonvulsants, muscle relaxants GABAA agonists – bind to receptor and facilitate effects of GABA; highly addictive Serotonin agonists (buspirone, SSRI) Reduce anxiety without sedation, side effects Copyright © 2009 Allyn & Bacon Neural Bases of Anxiety Disorders Drugs suggest a role for serotonin and GABA Amygdala, due to its role in fear and defensive behavior, thought to be involved No pathology yet identified Difficult to study neural basis of anxiety Diversity and subtlety of symptoms Abnormal breathing in anxious patients complicates functional brain imaging Copyright © 2009 Allyn & Bacon Tourette Syndrome A disorder of tics (involuntary movements) or vocalizations Begins in childhood Major genetic component Many also have signs of ADHD and/or OCD No animal models, no genes identified, imaging difficult due to tics Copyright © 2009 Allyn & Bacon Tourette Syndrome: Treatment Usually treated with neuroleptics – although effectiveness is not well-established Effectiveness of D2 blockers suggests abnormality in basal ganglia-thalamus-cortex feedback circuit Perhaps a neurodevelopmental disorder from excessive dopaminergic innervation of the striatum and associated limbic cortex DBS Deep brain stimulation looks promising DBS case Copyright © 2009 Allyn & Bacon