Schizophrenia - biological explanations

• Genes


  DNA strands that produce instructions for physical features, including mental health
• Schizophrenia has been noted to run in families, highlighting a familial link
• Schizophrenia is thought to be inherited through the generations through transmission of genes / DNA
• Children with two schizophrenic parents

  • 46% concordance rate
• Children with one schizophrenic parent

  • 13% concordance rate
• First-degree relatives of those with schizophrenia


  • 18 times more at risk than the general population
• Monozygotic (MZ/identical) twins


  Share 100% of their genes
• Dizygotic (DZ/fraternal) twins

  Share 50% of their genes
• Concordance rate for MZ twins

  • 40.4%
• Concordance rate for DZ twins

  • 7.4%
• Gottesman - Concordance rate for MZ twins

  • 48%
• Gottesman - Concordance rate for DZ twins

  • 17%
• Concordance rate for parents

  • 6%
• Concordance rate for first cousins

  • 2%
• Candidate genes

  Individual genes associated with the risk of inheritance of schizophrenia
• In the 1980's research focused on identifying the individual genes associated with developing schizophrenia, such as the C4, HLA and PCM1 genes
• Polygenic


  Schizophrenia is caused by a number of genetic mutations which when combined in an individual create a high risk that they could develop the disorder
• Schizophrenia is aetiologically heterogeneous - different combinations of these factors can lead to the development of the condition
• Genetic mutations can cause neural pathways in the brain to be disrupted or damaged
• Ripke et al (2014) looked at the genetic makeup of 37,000 patients and compared this to that of 113,000 control patients. 108 separate genetic variations were associated with the increased risk of schizophrenia
• Twins separated at birth who went on to experience schizophrenia

  21% more likely to have a biological relative with schizophrenia than their adopted family, who had a rate of 5%
• Children of schizophrenic parents

  Still at risk of schizophrenia even when adopted
• It is impossible to isolate the effects of genes (nature) from the environment (nurture), when studying human behaviour
• Joseph - MZ twins are treated more similarly, encounter more similar environments, are more likely to do things together and have the same friends and experience more identity confusion (being treated as 'twins' rather than individuals) than DZ twins
• Sekar et al. (2016) carried out genetic analysis on 65,000 people and found that those who had particular forms of the C4 gene showed a higher risk of developing schizophrenia
• Neural correlates


  Measurements of the structure or function of the brain that correlate with an experience
• Avolition involves the loss of motivation. Motivation is linked to the anticipation of a reward which is associated with the ventral striatum
• Abnormal functioning in the ventral striatum leads to the development of avolition
• Juckel (2006) found lower levels of activity in the ventral striatum in patients with schizophrenia compared to a control group, and a negative correlation between activity levels in the ventral striatum and the severity of overall negative symptoms
• Allen et al (2007) found lower activation levels in the superior temporal gyrus and anterior cingulate gyurs in patients experiencing auditory hallucinations compared to a control group
• Reduced activity in these two areas of the brain is a neural correlate with positive symptoms / auditory hallucinations
• It is difficult to establish cause and effect with neural correlates - it is unclear whether the unusual brain activity causes the symptoms or the symptoms lead to the brain activity
• Evidence for neural correlates


  • Comes from objective brain scans in highly controlled environments with specialist equipment, suggesting reliable and credible results