Theories of schizophrenia

• Biological (genetic data)

  There's a really convincing body of evidence indicating a predisposition for schizophrenia.

  • Family studies: revealing an increased risk for schizophrenia in relatives of those individuals who have schizophrenia.
  • Twin studies: concordance rates are much higher for identical twins than fraternal twins.
  • Adoption studies: studies of adopted children demonstrate a high rate of schizophrenia among the biological children of individuals with schizophrenia even when they’re reared by healthy adoptive parents.
• Biochemical factors (Dopamine)

  Excessive amounts.

  The dopamine hypothesis is the longest-standing biologically based theory of schizophrenia, and it has predominated for over four decades.

  Initially, the hypothesis that schizophrenia is related to excessive activity of dopamine is based principally on the knowledge that drugs effective in treating schizophrenia reduce dopamine activity.
• amphetamine psychosis

  supports the dopamine theory but this may only apply to schizophrenia with positive symptoms.
• serotonin


  more related to negative symptoms
• observable brain pathology

  Controversy whether these abnormalities are localized or are widespread.

  Research suggests:

  • structural problems in limbic areas and the prefrontal cortex.
  • enlarged ventricles - found in 80% of individuals with schizophrenia.
  • deterioration or atrophy of brain tissue.
  • atrophy in the prefrontal areas.
• viral infection

  mid-trimester of fetal development.

  causes brain damage.

  • Hypothesis: early brain injury remains silent until the prefrontal cortex matures, typically in adolescence.