Biological explanations Flashcards
What is the genetic explanation of schizophrenia?
Several genes increase an individual’s overall vulnerability to developing schizophrenia
What has replaced the traditional correlational twin, family and adoption studies when studying genetics?
Gene mapping
What did Gottesman and Shields find?
If one MZ twin develops schizophrenia there is a 28% chance that the other twin will also develop the disorder
What did Sorri et al. find?
Performed a longitudinal study for 21 years on Finnish adoptees and found that adoptees with a high genetic risk of developing schizophrenia were more sensitive to non-healthy rearing patterns, suggesting that environmental factors (and their interaction with genetic factors) are important too
What is currently the biggest indicator/risk factor for schizophrenia?
VCFS - the gene for cleft pallet
What is the dopamine hypothesis?
One neural correlate explanation: Dopamine acts to increase the rate of firing of neurons during synapse, which enhances communication between neurons. However, if too much dopamine is released it can lead to the onset of schizophrenia
What dopamine releasing drug creates schizophrenic symptoms in non-schizophrenic patients?
L-dopa
What does Davis believe?
High levels of dopamine in the mesolimbic dopamine system are associated with positive schizophrenic symptoms while high levels in the mesocortical dopamine system are associated with negative symptoms
High levels of dopamine in the __________ dopamine system are associated with positive schizophrenic symptoms
Mesolimbic
High levels of dopamine in the __________ dopamine system are associated with negative symptoms
Mesocortical
Why is the neurotransmitter glutamate implicated in schizophrenia?
There is reduced function of the NMDA glutamate receptor in schizophrenics, and dopamine is involved in this system as dopamine receptors restrict the release of glutamate
What did Randrup and Munkvad do?
Created schizophrenic behaviour in rats by giving them amphetamines (activates dopamine production) and then reversed the effect by giving them neuroleptics (inhibits dopamine release)
What did Iversen find?
Post-mortems on people who had schizophrenia found excess dopamine in the limbic system
What do Lloyd et al. believe?
Even if dopamine is a causative factor, it may be an indirect factor mediated through environmental factors, because abnormal family circumstances can lead to higher dopamine levels which may in turn lead to the onset of schizophrenia
What is the neural correlate explanation?
Abnormalities within specific brain areas may be associated with the development of schizophrenia
What are ventricles?
Fluid-filled gaps between brain areas
What should be considered when discussing neural correlates?
Whether brain abnormalities are caused by genetic factors or as a result of the disorder
What does the neural correlates explanation see as the cause of positive symptoms of schizophrenia?
Overactive dopamine pathways in the mesolimbic area of the brain
What does the neural correlates explanation see as the cause of negative symptoms of schizophrenia?
Underactive dopamine pathways in the mesocortical area of the brain
What did Johnstone et al. find?
Schizophrenics had enlarged ventricles while non-sufferers did not, suggesting that schizophrenia is associated with a loss of brain tissue
What did Weyandt et al. find?
Enlarged ventricles are associated with negative symptoms only, which implies enlarged ventricles cannot explain all symptoms and incidences of schizophrenia
What did Hoek et al. find and what alternative biological explanation do they suggest?
Studied malnourished children in Holland after WWII and found that children born during or after the famine were 1.9/2.2 times more likely to develop schizophrenia; therefore suggests foetal malnutrition as the cause of schizophrenia
What did Bennedson et al. find?
Women with schizophrenia were more likely to give birth to a child of low birth weight (a factor implicated in schizophrenia) because women with schizophrenia were more likely to be smokers, have substance abuse and alcohol problems which stunt intrauterine growth
