12.2.1 The Genetic Basis of Schizophrenia

Biological explanations for schizophrenia:

A genetic explanation of schizophrenia

The genetic explanation of schizophrenia suggests that schizophrenia is inherited and polygenic.

Family studies show that the likelihood of developing schizophrenia increases the more closely related the individual is to a person with schizophrenia. This suggests that there is some genetic cause of schizophrenia.

Twin studies are used to test the genetic nature of schizophrenia. If there is a higher concordance rate between MZ twins than DZ twins it suggests that there is a genetic link

Adoption studies are also used to see if adopted children have similarities with their biological parents as this would suggest that it is inherited.

Evaluation:

1. Supporting evidence suggests there is a genetic link between family twin and adoption studies
2. Practical application – could help to see those at risk and do early intervention
3. Twin studies may be explained by environmental factors. For example, MZ (identical) twins are treated more similarly
4. It's difficult to separate the influences of nature and nurture. For example, the fact that concordance rates aren't 100% suggests that schizophrenia can't be wholly explained by genes. This suggests that genetic explanations can't give a full explanation of the disorder
5. Potentially family, twin and adoption studies may suffer from demand characteristics. This is because family members who may have been diagnosed may be biased in their diagnosis.
6. The doctor may be biased in giving a diagnosis if there is a family history of schizophrenia

Dopamine hypothesis:

Dopamine is an excitatory neurotransmitter (makes neurons fire). Linked to positive symptoms of schizophrenia

• Schizophrenia is a result of too much dopamine being produced, or oversensitivity of D2 receptors at the post-synaptic terminal L-dopa is a synthetic dopamine-releasing drug used to treat Parkinson's disease and was found to reduce schizophrenia-like symptoms. Other drugs include LSDC which acts on dopamine systems and can aggravate symptoms

Antipsychotic drugs have been successful in reducing symptoms of schizophrenia which have been found to inhibit dopamine activity, supporting the dopamine hypothesis

Hyperdopaminergia = excessive levels of dopamine in the subcortex and Broca's area. This is linked to positive symptoms

Hypodopaminergia = Low levels of dopamine in the prefrontal cortex. This is linked to negative symptoms