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Psychotic Disorders >> Schizophrenia (continued 3)

Epidemiology

  • prevalence: 0.5%-1%; M:F = 1:1
  • mean age of onset: females ~27; males ~21


Etiology

  • multifactorial: disorder is a result of interaction between both biological and environmental factors
    • genetic - 50% concordance in monozygotic (MZ) twins; 40% if both parents have schizophrenia; 10% of dizygotic (DZ) twins, siblings, children affected
    • neurochemistry – “dopamine hypothesis” theory: excess activity in the mesolimbic dopamine pathway may mediate the positive symptoms of psychosis (i.e. delusions, hallucinations, disorganized speech and behaviour, and agitation)
    • neuroanatomy - decreased frontal lobe function, asymmetric temporal/limbic function, decreased basal ganglia function; subtle changes in thalamus, cortex, corpus callosum, and ventricles; cytoarchitectural abnormalities
    • neuroendocrinology - abnormal growth hormone, prolactin, cortisol, and adrenocorticotropic hormone
    • neuropsychology - global defects seen in attention, language, and memory suggest lack of connectivity of neural networks
    • indirect evidence of geographical variance, winter season of birth, and prenatal viral exposure


Pathophysiology

  • neurodegenerative theory
    • natural history may be rapid or gradual decline in function and ability to communicate
    • glutamate system may mediate progressive degeneration by excitotoxic mechanism which leads to production of free radicals
  • neurodevelopmental theory - abnormal development of the brain from prenatal life
    • neurons fail to migrate correctly, make inappropriate connections, and break down in later life
    • inappropriate apoptosis during neurodevelopment resulting in faulty connections between neurons

Clinical Pearl

Supportive Evidence for Dopamine Hypothesis

Dopamine (DA) agonists exacerbate schizophrenia
Antipsychotic drugs act by blocking post-synaptic DA receptors
Potency of many antipsychotic drugs correlates with D2 blockade of post-synaptic receptors
Antipsychotic drugs are associated with an increase in the number of D2 and D4 post-synaptic receptors

 

Related Links :

Schizophrenia

Schizophrenia (continued 1)
Schizophrenia (continued 3)

Schizophrenia (continued 4)

 

Psychotic Disorders >> Links :
Definition
Differential Diagnosis of Psychosis

Schizophreniform Disorder
Brief Psychotic Disorder
Postpartum Mood Disorders

Schizoaffective Disorder
Delusional Disorder
Shared Psychotic Disorder (Folie à Deux)
Psychotic Disorders >> Schizophrenia (continued 3) Psychotic Disorders >> Schizophrenia (continued 3) Reviewed by Radiology Madeeasy on April 09, 2011 Rating: 5
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