SZ: Biological explanations Flashcards
Name the two/three theories of biological explanations
-Neural correlates (important: the dopamine hypothesis)
-Genetic inheritance
Dopamine hypothesis A01
Original-excess of dopamine (hyperdopaminergia) in the sub-cortical areas (mesolimbic pathway, broca’s area) result in hallucinations and delusions
Revised- Deficit(hypodopaminergia) in pre-frontal cortex results in negative symptoms
Genetic inheritance A01
-SZ inherited as a result of genotype- is polygenic
-As genetic similarity increases, probability of sharing SZ increases (Gottesman). Population rate starts at 1% Shows bio factor is involved
Neural correlates A01
The ventral striatum- negative symptoms of schizophrenia e.g. avolition, as VS is part of limbic system associated with anticipation of reward
The superior temporal gyrus (STG), which is thought to control the processing of speech-positive symptoms of schizophrenia e.g. hallucinations
Neural correlates A03
Schizophrenic patients show less activity in the VS which is associated with apathy (Kirschener et al. 2016)
Schizophrenic patients show reduced volume of grey matter in the STG- associated with hallucinations and thought disorder (Rajarethinam et al. 2000)
Dopamine hypothesis A03
-Supported by drug treatment: Amphetamines (dopamine agonists) result in SZ like symptoms, chloroprozamine reduces pos sympoms. Validates.
-However 30% of SZ patients not affected by CHP, suggests other causes- hypothesis is reductionist
-Practical app- lead to development of a-typical antipsychotics
Gen inheritance A03
-Supported by twin studies: 40% concordance with MZ, 7% concordance with DZ
However-
Cardno et al- meta-analysis- varying concordance rates of 41-65% in MZ due to different ways of calculating concordance. Reduces reliability. + not 100%- suggests other factors
Issue and debate of biological explanations
-Bio reductionist
-Deterministic
-Nature vs nurture
