principles

• dopamine hypothesis


  people with schizophrenia have excess amounts of dopamine in the limic system
• revised dopamine hypothesis 


  there is an excess amount of dopamine receptors in the post synaptic neurone which are more sensitive so dopamine is absorbed in various pathways

  excess receptors can be due to injury, disease or genetics
• seeman evidence for dopamine hypothesis

  drugs that increase dopamine increased positive symptoms such as hallucinations

  antipsychotic drugs which block dopamine receptors reduced symptoms

  post mortems of brains with schizophrenia show higher density of D2 receptors than neurotypical brains
• grey matter


  enlarged ventricles of schizophrenic brains lead to less grey matter

  temporal lobe = verbal and acoustic memory so auditory hallucinations

  thalamus = relay station of motor movement which explains hallucinations (hearing, touch, sight, taste)

  frontal lobe = planning coordination which explains incoherent speech and perceptual disturbances
• brain size


  reduced overall size of the brain in schizophrenic brains with less grey matter than neurotypical brains

  correlation between less grey matter and length of time with schizophrenia

  reduction stops when patients taken antipsychotics which reduces symptoms
• pol et al


  tested 159 brains with schizophrenia and 158 neurotypical brains

  found an increase by 30% of ventricle size and a reduction in grey matter
• haijma 


  meta analysis on 317 studies using MRI scans using 8000 people with schizophrenia

  found that patients with schizophrenia are 2.6% smaller

  brain areas like the thalamus which deal with sensory and motor integration were smaller in people who hadnt recieved treatment for schizophrenia
• ventricle size


  people with schizophrenia have enlarged ventricles

  could explain cognitive symptoms such as disorganised speech

  four ventricles hold cerebral spinal fluid which provide nutrients and protect the brain
• positive symptoms


  hypofunction of dopamine in the mesolimic pathway

  responsible for motivation, emotion and rewards

  can explain positive symptoms of schizophrenia
• negative symptoms


  erratic dopamine in the mesolimic pathway

  can explain cognitive deficits and problems with affects during an episode

  responsible for executive funtion, mental control and self regulation
• adoption studies


  Tienari found that the lifetime risk of adopted children with schizophrenic biological mothers was 9.4%

  strong genetic component

  adpoted children with unaffected parents was 1.2%
• twin studies


  concordance for DZ twins = 15%

  concordance for MZ twins = 46%-53%

  strongly implies a genetic component to schizophrenia
• family studies


  Gottesman and Shields - found that MZ twins had a higher concordance rate for both having schizophrenia than DZ twins

  Gottesman - increased risk of developing schizophrenia if parents have schizophrenia (7%)

  Riley and Kendler - the risk is ten times greater for first degree relatives of someone with schizophrenia
• association studies


  Ripke - genome wide study with 36000 schizophrenia patients and 113000 non affected, found 108 separate genetic variations increasing risk

  multifactional polygenic model suggests many individual genes carry a small risk of schizophrenia