Biological explanation of schizophrenia - A-Level Psychology
The genetic basis for schizophrenia:
-schizophrenia runs in families.This is weak evidence in itself for a genetic link because family members tend to share an environment as well as many of their genes. However,there have been systematic investigations of the extent to which greater genetic similarity between family members is associated with the likelihood of both developing schizophrenia.
-there is a strong relationship between the degree of genetic similarity and shared risk of schizophrenia.
Gottesman (1991):
-large-scale family study.
-found that the concordance rate for schizophrenia in MZ twins was 48% compared to 17% for DZ twins.
Candidate genes:
-schizophrenia is polygenic.
-different studies have identified different candidate genes so it appears that schizophrenia is aetiologically heterogeneous(different combinations of factors can lead to the condition).
Stephen Ripke et al(2014)-carried out a huge study combining all previous data from genome-wide studies of schizophrenia.The genetic makeup of 37000 patients was compared to that of 113000 controls;108 separate genetic variations were associated with increased risk of schizophrenia.
Genes associated with increased risk included those coding for the functioning of a number of neurotransmitters including dopamine.
The dopamine hypothesis:
Neurotransmitters-the brain’s chemical messengers appear to work differently in the brain of a patient with schizophrenia.Dopamine is widely believed to be involved.It is important in the functioning of several brain systems that may be implicated in the symptoms of schizophrenia.
Hyperdopaminergia in the subcortex-original version of the dopamine hypothesis focused on the possible role of high levels of dopamine in the subcortex(central areas of the brain).For example,an excess of dopamine receptors in Broca’s area(speech production) may be associated with speech poverty and the experience of auditory hallucinations.
Hypodopaminergia in the cortex–more recent versions of the dopamine hypothesis focus on abnormal dopamine systems in the brain’s cortex.Goldman-Rakic et al.(2004) identified a role for low levels of dopamine in the prefrontal cortex(responsible for thinking and decision making) in the negative symptoms of schizophrenia.
It may be that both these explanations are involved in schizophrenia.
Neural correlates of schizophrenia:
-are measurements of the structure/function of the brain that correlate with an experience.
-both positive and negative symptoms have neural correlates.
Neural correlates of positive symptoms:
-Avolition involves the loss of motivation.Motivation anticipates the anticipation of a reward .The ventral striatum is believed to be involved with this anticipation.So,abnormality in the ventral striatum may be involved in the development in avolition.
-Juckel et al measured activity levels in the ventral striatum in schizophrenia and found lower levels of activity than those in controls.They observed a negative correlation between activity levels in the ventral striatum and the severity of negative symptoms.
Neural correlates of positive symptoms:
-Allen et al scanned the brains of patients experiencing auditory hallucinations and compared them to a control group whilst they identified pre-recorded speech as theirs or others.Lower levels of activity in the superior temporal gyrus and anterior cingulate gyrus were found in the hallucination group that made more errors.
Evaluation:
The correlation-causation problem-there are a number of neural correlates of schizophrenia symptoms.It may be that unusual activity in those regions cause the symptom or the other way around.
Mixed evidence for the dopamine hypothesis-Dopamine agonists increase the levels of dopamine and make schizophrenia worse and can produce schizophrenia-like symptoms in non-sufferers.Antipsychotic drugs reduce dopamine activity.These suggest an important role of dopamine in schizophrenia .Lindstroem et al found that chemicals needed to produce dopamine are taken up faster in the brains of schizophrenia sufferers than control suggesting that they produce more dopamine.There may be other neurotransmitters involved such as glutamate.
There is evidence to suggest that multiple genes may be involved in the development of schizophrenia, although no specific “schizophrenia gene” has been identified. However, studies have shown that individuals with a family history of schizophrenia are more likely to develop the disorder themselves, suggesting that genetic factors play a role.
Neurobiological factors, such as changes in brain structure and function, are thought to contribute to the development of schizophrenia. For example, some studies have found that individuals with schizophrenia have reduced gray matter volume in certain brain regions, as well as abnormalities in neurotransmitter systems such as dopamine and glutamate.
While genetic and neurobiological factors are believed to play a primary role in the development of schizophrenia, there is also evidence to suggest that environmental factors may contribute as well. For example, prenatal exposure to viral infections or maternal stress has been associated with an increased risk of developing schizophrenia.
Treatment for schizophrenia typically involves a combination of medication and psychotherapy. Antipsychotic medications can help alleviate symptoms such as delusions and hallucinations, while psychotherapy can help individuals learn coping skills and improve social functioning.
There is currently no cure for schizophrenia, but with proper treatment, many individuals with the disorder are able to manage their symptoms and lead fulfilling lives. Early intervention and ongoing treatment are key to achieving the best outcomes.
Substance abuse, particularly of drugs such as marijuana and cocaine, has been associated with an increased risk of developing schizophrenia. Additionally, individuals with schizophrenia are more likely to struggle with substance abuse, which can exacerbate their symptoms and make treatment more difficult.
Research into the genetic and neurobiological factors underlying schizophrenia is ongoing, and new findings are emerging all the time. Additionally, there is increasing interest in the role of early intervention and personalized treatment approaches in improving outcomes for individuals with the disorder.
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