chapter 16 notes

chapter 16 notes - CHAPTER 16: Schizophrenia and the...

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CHAPTER 16: Schizophrenia and the Affective Disorders Schizophrenia affects approx 1% of world's population. Has been around for 1000s of years. “Schizophrenia” means “split mind”, but does not imply a split or multiple personality. Eugen Bleuler coined the term: meant it to refer to a break w/ reality caused by disorganization of various functions of the mind, such that thoughts/ feelings no longer work together normally. Characterized by universal symptoms of disordered thoughts, delusions, hallucinations, and often bizarre behaviors. There are 3 categories of schizophrenia symptoms: 1. positive symptoms: make themselves known by their presence. Includes hallucinations (most commonly voices or olfactory), thought disorders (disorganized, irrational thinking), and delusions (of persecution, grandeur, and control). 2. negative symptoms: known by absence of normal behaviors. Includes flattened emotional response, poverty of speech, lack of initiative and persistence, anhedonia, social withdrawal. 3. cognitive symptoms: Includes difficult in sustaining attention, low psychomotor speed (ability to rapidly/fluently perform movements of fingers, hands, legs), deficits in learning and memory, poor abstract thinking, and poor problem solving. Symptoms typically appear gradually over 3-5 yrs: 1 st positive, then cognitive; positive yrs later. Heritability: Both adoption and twin studies indicate that schizophrenia is a heritable trait. The incidence of schizophrenic children of 2 schizophrenic parents is less than 50% → This means either several genes are involved or that having a “schizophrenia gene” imparts a susceptibility to develop the disorder, the disease itself being triggered by other factors. Test for susceptibility hypothesis: studies found that percentage of schizophrenic children was identical for both the non- schizophrenic and the schizophrenic twin of a pair. This provides evidence for heritability, and that carrying the “gene” does not necessarily lead to the disorder. Another genetic factor is paternal age. Children of older fathers= more likely to develop schizophrenia; this increased incidence is believed to be caused by mutations in spermatocytes (cells that produce sperm); sperm divide many times, which increases room for DNA errors. Candidates for “schizophrenia gene”: (no single one; a large # of rare mutations is suggested). Mutations of DISC1 ( disrupted in schizophrenia 1 ), a gene involved in regulation of neuronal migration during development, have been found in families w/ high incidences of schizophrenia. Studies suggest that epigenetic mechanisms (which control expression of genes) may contribute to development of schizophrenia as well as mutations. Eg: long DNA strands that constitute chromosomes are wound around
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chapter 16 notes - CHAPTER 16: Schizophrenia and the...

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