Biological Explanations of Schizophrenia

Topics: Schizophrenia, Dopamine, Antipsychotic Pages: 6 (1954 words) Published: February 21, 2014
Describe and evaluate biological explanations of schizophrenia (24 marks) Schizophrenia is a psychotic disorder characterized by distorted thinking, impaired emotional responses, poor interpersonal skills and a distortion of reality. It is the most common of psychotic disorders that, in most countries around the world, affects around 1 per cent of the population. In terms of explanations for the disorder, two central types of explanations arise – psychological explanations and biological explanations. Whereas psychological explanations tend to focus on cognitive, emotional and environmental factors that may cause the disorder, biological explanations tend to focus on genetic, biochemical and neuro-anatomical factors as the cause of the disorder. One biological explanation of schizophrenia is ‘the genetic hypothesis’. Schizophrenia appears to run in families, and Gottesman (1991) has shown through a series of controlled genetic correlational studies that the likelihood of an individual developing schizophrenia is proportional to the amount of genes they share with somebody affected by schizophrenia. For example, children with two schizophrenic parents have a concordance rate of 46 per cent, monozygotic (MZ) twins have a concordance rate of 48 per cent, and dizygotic (DZ) twins have a concordance rate of 17 per cent. However, from these studies it has also been made clear that genetic factors cannot be the only explanation for schizophrenia. Although genetic studies support the argument for a genetic basis for the disorder, they have also shown that even when the relative is genetically identical – like monozygotic twins – the chance of developing schizophrenia is below 50 per cent. This implies therefore, that heredity factors are not the primary cause of schizophrenia, other factors are clearly involved. In addition to this, many researchers have suggested that the reason that schizophrenia appears to run in families could be due to common rearing patterns and that genetic factors are comparatively uninvolved. Research on expressed emotion shows that negative emotional climates that are high in expressed emotion could lead to stress beyond an individual’s coping mechanisms, and could thus trigger a schizophrenic episode (Linzen et al, 1997), further exemplifying the importance of environmental factors in the onset of schizophrenia. In an attempt to disentangle controversy surrounding genetic and environmental factors, twin studies and adoption studies have been carried out. With twin studies the underlying assumption has been that monozygotic twins will show a greater concordance rate than dizygotic twins as they are genetically identical, and many studies have supported this assumption. Although many twin studies do consistently reveal a greater concordance rate in monozygotic twins than dizygotic twins, the extent to which this is the case varies greatly. For example, Cardno et al (2002) showed a concordance rate of 26.5 per cent for monozygotic twins and 0 per cent for dizygotic twins based on the ‘Maudsley Twin Register’, compared to Joseph (2004) who, when using pooled data for all schizophrenia twin studies carried out prior to 2001, found a concordance rate of 40.4 per cent in monozygotic twins and 7.4 per cent for dizygotic twins. There are several issues with this kind of research, however. As only 1 per cent of the population is schizophrenic and around 0.3 per cent of the population are monozygotic twins, statistically only 0.003 per cent of the entire population is a schizophrenic monozygotic twin. This means that sample sizes in these studies are usually very small and so researchers have difficulty generalizing results to the entire population. In addition, twin studies do not all use the same diagnostic criteria and so comparisons cannot always be made (McGuffin et al, 1984), and concordance rates can be calculated in different ways and vary depending on the method used – meaning that twin studies can...
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