biological explanations Flashcards
(16 cards)
What have family studies shown about genetics and schizophrenia?
Gottesman - the closer the degree of genetic relatedness, the greater the risk
Found children with:
2 schizophrenic parents = 46% concordance rate
one schizophrenic patient = 13% concordance rate
Siblings = 9% concordance rate
What have twin studies shown about genetics and schizophrenia?
Joseph - greater similarity of genetics = greater likelihood of developing schizophrenia
MZ twins = 40.4% concordance rate
DZ twins = 7.4% concordance rate
What have adoption studies shown about genetics and schizophrenia?
Tienari et al - Finland
Of 164 adoptees whose biological mothers had schizophrenia, 6.7%also received a diagnosis of schizophrenia compared to 2% of control group
Demonstrates genetic liability
What does the dopamine hypothesis suggest?
An excess of the neurotransmitter dopamine in certain regions of the brain is associated with positive symptoms
Schizophrenics are thought to have high D2 receptors on receiving neurons = more dopamine binding = more dopamine firing
What is an example of a drug that increases dopaminergic activity and how does it work?
Amphetamine is a dopamine agonist i.e. stimulates nerve cells containing dopamine, causing the synapse to be flooded with this neurotransmitter - ‘normal’ individuals exposed to large doses of dopamine experience schizophrenic symptoms
How do drugs that decrease dopaminergic activity work?
Block activity of dopamine in the brain - dopamine antagonists because they block its action - alleviate symptoms of schizophrenia
Who proposed the revised dopamine hypothesis and what does it suggest?
Davis & Kahn - proposed positive symptoms of schizophrenia are caused by an excess of dopamine in subcortical area of the brain, particularly the mesolimbic pathway
Negative symptoms are thought to arise from a deficit of dopamine in areas of the prefrontal cortex
What specific areas of the brain are involved in schizophrenia?
Prefrontal cortex
Hippocampus
Grey matter
White matter
How is the prefrontal cortex involved in schizophrenia?
Hypofunction (reduced activity) in the prefrontal cortex is associated with negative symptoms of schizophrenia
How is the hippocampus involved in schizophrenia?
Goto and Grace suggest hippocampus dysfunction can influence levels of dopamine in the basal ganglia indirectly affecting the processing of information in the prefrontal cortex
How is grey matter involved in schizophrenia?
People with schizophrenia often show a reduction in grey matter volume, especially in the prefrontal cortex and temporal lobes.
This reduction is linked to negative symptoms (e.g. lack of emotion, poor social functioning) and cognitive deficits.
How is white matter involved in schizophrenia?
Disrupted white matter pathways (especially in areas like the corpus callosum) can lead to poor inter-region communication in the brain.
This may explain disorganized thinking, poor attention, and auditory hallucinations.
What’s an evaluation point of the twins study?
MZ twins are treated more similar, encounter more similar environments and experience more ‘identity confusion’ (treated as twins rather than distinct people)
Environmental differenced between Mz and DZ twins more important?
Who challenges the dopamine hypothesis and how?
Noll - Antipsychotic drugs do not alleviate hallucinations and delusions in about 1/3 of people experiencing them + hallucinations and delusions are often present despite levels of dopamine being normal -proves dopamine is no the sole cause of positive symptoms
What evidence is the antipsychotics that reduce dopamine work?
Leucht et al: meta-analysis of 212 studies and concluded the antipsychotics tested were significantly more effective than the placebo - demonstrates dopamine is a causing factor
What are the implications of such research for treatments?
‘treatment as prevention’ (Addington) which uses a number of different assessments e.g. neuroimagaing to predict who will develop psychoses such as schizophrenia
With a better understanding - of how schizophrenia develops + detect and treat at risk patients before developing psychosis
