Biological explanations

• Family studies into schizophrenia

  Gottesman's large-scale family study (1991) confirmed risk of schizophrenia increases in line wth genetic simularity, however family members tend to be exposed to the same enviroment causing a correlation between genetics and enviroment.
• Candiate genes

  Multiple gees are involved in the diagnosis of schizophrenia (it is polygenic)

  Ripke et al (2014) conclded that schizophrenia is aetiologically heterogeneous (combination of factors e.g. genetic variation
• Mutation in schizophrenia

  Can be caused by mutated parental DNA (radiation, poison or infection)
• Twin studies in SZ

  Joseph (2004) - MZ twins are treated much more similarly than DZ twins as they are treated more as a pair than individuals.
• Adoption studies

  Tienari et al ( 2000) found that 164 adoptees whos biological mothers had SZ , 6.7% also received a diagnosis compared to 2% of the 197 'control' adoptees (born to non- SZ mothers)
• Environmental factors affecting SZ.

  Clear evidence showing that environmental factors also alter the risk of a diagnosis. Morgan et al (2017) - smoking THC rich cannabis in teenage years, Di Forti et al (2015) Childhood trauma.

  Morkved et al (2017) found that 67% of SZ patients reported at least one childhood trauma as opposed to the 38% of a matched group with no mental health issues.
• The role of dopamine

  Dopamine is responsible for feelings of pleasure. It effects thinking and movement.
• What is Hyperdopaminergia?

  High levels of dopamine in the sub cortex, an excess of dopamine receptors in the Broca’s area may be associated with speech poverty and auditory hallucinations.
• What is Hypodopaminergia?

  Low levels of dopamine in the cortex. linked to the negative symptoms of SZ (Goldman-Rakic, 2004)
• David and Kahn (1991) research into dopamine.

  Positive symptoms caused by and excess of dopamine in the subcortical areas of the brain (ie. the mesolimbic pathway)

  Negative symptoms = deficit of dopamine in the prefrontal cortex (mesocortical pathway)
• Research support for the dopamine hypothesis.

  Drug therapy.

  L dopa - parkinsons medication, increases dopamine which may produce symptoms similar to that of SZ
• Limitations of the dopamine hypothesis.

  Drugs were ineffective for 1/3 of patients. Suggesting dopamine cannot explain all cases.