Schizophrenia- Biological Explanations Flashcards
What is the biological explanation?
Everything psychological is at first biological
What is concordance rates?
Probability that a pair of individuals will both have a certain characteristic, given that one of the pair has the characteristic
Gottesman:
MZ twins= 48% concordance rate
DZ twins= 17% concordance rate
Parents= 6%
Does Gottesman support the biological explanation?
Yes
It supports the biological explanation as the closest genetic similarity, the higher concordance rates
Adoption studies
Tienari et al: out of 164 adopted children whose birth mothers had been diagnosed with SZ, 6.7% of children shared this diagnosis compared to only 2% out of 197 children with non-SZ birth mothers
Candidate genes
Schizophrenia is polygenic
Ripke et al: 108 separate genetic variations were associated with increased risk of schizophrenia
Dopamine hypothesis
A theory that dopamine abnormalities in the brain cause a psychosis
Dopamine hypothesis:
Excess of dopamine
Ventral Tegmental Area - Nucleus Accumbens
Overactivity of the mesolimbic pathway; causes positive symptoms of schizophrenia due to excess levels of dopamine
Dopamine hypothesis:
Deficiency of dopamine
Ventral Tegmental Area - Pre Frontal Cortex
Mesocortical pathway dysfunction; causes negative and cognitive symptoms due to the deficiency of dopamine
Neural correlates:
Ventricular enlargement
Johnstone et al (1976): schizophrenia patients had enlarged ventricles in the brain compared to those without schizophrenia. Suggets a decreased volume of frontal and temporal lobe is linked to schizophrenia
Brown et al (1986): decrease brain weight and enlarged ventricles in schizophrenia patients
Neural correlates:
Decreased size of cortex
Thompson et al (2001): MRI found a greater loss of cerebral cortex tissue between 13-18 in adolescents with rare childhood on-set schizophrenia
Neural correlates:
Cellular disarray in hippocampus
Decrease in size of the hippocampus; control emotions and working memory
