Biological explanations for schizophrenia: Flashcards
genetics and neural correlates, including the dopamine hypothesis.
explain the genetic explanation for schizophrenia
suggests that schizophrenia is inherited
polygenetic disorder - multiple genes are associated with a higher risk of developing schizophrenia
high concordance rates in closely related families
research evidence for genetic explanation of schizophrenia - twin studies
Gottesman (1991) reviewed cases of schizophrenia in twins
found concordance rate of 48% in MZ twins, 17% in DZ twins compared to 1% in general population
MZ and DZ twins usually share similar environment so result suggest schizophrenia has a genetic aspect but not fully genetic
research evidence for genetic explanation of schizophrenia - family studies
Gottesman (1991) reviewed cases of schizophrenia in families
found that children with 2 schizophrenic parents had a concordance rate of 48% and those which 1 schizophrenic parent was 13% and those with siblings with SZ was 9%
research evidence for genetic explanation of schizophrenia - adoption studies
Tienari (2004) studied the biological children of schizophrenic mothers who had been adopted
found that 5.8% of children adopted into psychologically healthy families development schizophrenia compared to 36.85 that were raised in dysfunctional families
as the risk is above the general population (1%) this suggests a genetic basis but an argument could be made for psychological factors too
what are neural correlates?
patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience
explain the neural explanation for schizophrenia
The dopamine hypothesis suggests that symptoms of schizophrenia are associated with an imbalance of the neurotransmitter dopamine in the brain
hyperdopaminergia - too much dopamine in Broca’s area - may lead to auditory hallucinations (positive symptoms)
hypodopaminergia - too little dopamine in frontal cortex - may lead to avolition or speech poverty (negative symptoms)
how did the dopamine hypothesis come about?
from observations that found dopamine releasing drugs e.g. L-dopa can produce schizophrenic-like symptoms in healthy patients and anti-psychotic drugs e.g. phenothiazine decrease symptoms of SZ and reduce dopamine levels
what are other neurotransmitters that may explain SZ?
glutamate - excitatory neurotransmitter - involved in learning, attention and memory - low levels in people with SZ
serotonin - found to effect SZ - led to development of treatments like clozapine
research evidence for neural correlates - the dopamine hypothesis
Patel et al (2010) used PET scans and found lower dopamine levels in prefrontal cortex of people with SZ compared to ‘normal’ controls
evaluations of genetic explanations of SZ
+ strong evidence for genetic vulnerability to SZ - Gottesman (family and twins) and Tienari (adoption studies) - suggests genetic factors make people more vulnerable
- biological reductionist - evidence to show environmental factors increase risk of developing SZ - e.g. birth complications, smoking THC-rich cannabis, childhood trauma - study found 67% of people with SZ reported childhood trauma compared to 38% in non-psychotic group - genetic factor is not the only factor
+- suggests a diathesis-stress model can explain SZ - holistic
evaluations of neural explanations of SZ
+ evidence from drug studies supporting abnormal dopamine functioning - dopamine agonists e.g. amphetamines increase dopamine levels making SZ worse or producing SZ-like symptoms in people without SZ and antipsychotic drugs reduce dopamine activity and are used as an effective treatment for people with SZ - suggests dopamine is involved in symptoms of SZ
- evidence for a central role of glutamate - post-mortem and live-scanning studies found raised levels of glutamate in brains of people with SZ - several candidate genes are believed to be involved in glutamate production - dopamine is not the other neurotransmitter affecting SZ
