Biological explanations

• The genetic explanation for schizophrenia suggests that it is inherited and results from a biological process driven by an activity of certain genes, such as brain structure for development and neurotransmitter levels.
• Schizophrenia is said to be polygenic as multiple genes contribute to the development of the disorder.
• Ripke (2014) conducted a genetic analysis of over 36 thousand schizophrenia cases and identified a 108 gene loci associated with the development of schizophrenia. This suggests a range of genes are responsible for the disorder but also suggests the disorder is aetiologically heterogenous as different combinations of genes are correlated with having the disorder.
• Neural correlates are the variations in neural structure and bio chemistry that are correlated with an increased risk of developing schizophrenia.
• The dopamine hypothesis suggests that symptoms of schizophrenia are associated with too much or too little of the neurotransmitter across the brain.
• Hyperdopaminergia is having excess amount of dopamine in speech centres in the brain, like the Broca's area, leading to auditory hallucinations.
• Hypodopaminergia is having low levels of dopamine in areas of the frontal cortex thought to lead to negative symptoms such as avolition or speech poverty.
• Locations of positive symptoms:

  • Auditory hallucinations - Superior temporal gyrus and anterior cingulate gyrus.

  This was found through the use of brain scans conducted by Allen.
• Locations of the negative symptoms:

  • Avolition - Ventral striatum.

  This was found through brain scans conducted by Juckel.
• Strengths of the biological explanation for schizophrenia:

  • Supporting evidence - Leueht conducted a meta-analysis review of 212 studies. These studies assessed the effectiveness of biological anti-psychotic drugs treatments that work by normalising the levels of dopamine. Findings showed the drugs were more effective than placebos, suggesting the influence of the dopamine system has validity.
• Strengths of the biological explanation for schizophrenia:

  • Strong evidence base - Tienari (2004) conducted adoption studies where he found children with parents with schizophrenia has genetic vulnerability to the condition. 6.7% of children who had a biological mother with schizophrenia also developed the disorder compared to the 2% or children who did not have either.
• Strengths of the biological explanation for schizophrenia:

  • Support for the dopamine hypothesis - Curran found Amphetamines increase the dopamine production in the brain, mimicking symptoms of the disorder, while Tauscher found Anti-psychotics reduce the intensity of the symptoms. As we know candidate genes act of the production of dopamine and its receptors, this suggests that dopamine is heavily involved in the symptoms of schizophrenia.
• Limitations of the biological explanations of schizophrenia:

  • Counter evidence for the role of the environment - Morgan found biological risks, such as birth complications, contribute to the development of the disorder. DiForti also found the same results in individuals who smoked TCH-rich cannabis during teenage years. Morkved found psychological risk factors, including childhood trauma, also contribute to it (67% of patients reported at least one childhood trauma). This means the biological explanations alone are very limited and reductionist.
• Limitations of the biological explanations of schizophrenia:

  • Evidence for the role of glutamate - McCutcheon (2010) found raised levels in glutamate in patients with schizophrenia. There was also several candidate genes for the production of the glutamate. This means a strong case can be made for the role of other neurotransmitters in the development of the disorder.