‘Research into schizophrenia shows that there is a major genetic component but the fact that concordance rates between identical twins is never 100% means that there must be environmental contributions.’ Discuss biological explanations of schizophrenia. (30 marks) Schizophrenia is a psychiatric disorder involving the loss of contact with reality and a range of symptoms. There is considerable evidence that genetic factors are involved. This view considers that certain individuals possess certain genes which predispose them to schizophrenia. This means that it is inherited and we would expect to find that relatives have similar chances of developing the disorder. Indeed research has found that first degree relatives of people with schizophrenia are 18 times more likely to be affected than the general population.
Monozygotic twins would be expected to have the same chance of having schizophrenia as they carry the same genes. Research by Gottesman and Shields has found high concordance rates (where both twins have the disorder) in monozygotic twins than in dizygotic. However if schizophrenia was solely caused by genes then we would expect a 100% concordance in monozygotic twins. Since this is not found then other factors must play a part.
Mz twin studies have the advantage of controlling for genetics but the disadvantage of not controlling for environment. One way to get around this is to study mz twins that were raised apart. Twin studies show similar concordance rates even when they have been reared apart, however the samples use din these studies are usually very small and family problems may have been the reason for separation.
A genetic predetermination could lead to abnormalities in the brain. There is strong support for the idea that high dopamine levels are involved in schizophrenia. Dopamine functions as a neurotransmitter in the brain and autopsies have found high levels in the brains of schizophrenics. Research on amphetamines supports this because they increase the dopamine levels and have been found to worsen schizophrenic symptoms.
One study found that rats which had been given amphetamines displayed schizophrenic-type behaviour, though there is no reason to believe that humans react the same way as rats. It has also been found that those drugs that reduce dopamine (antipsychotic drugs). Also reduce schizophrenic symptoms. However, this tends to be correlational and we can’t know if dopamine levels cause schizophrenia or schizophrenia causes high dopamine levels. MRI scans have found that schizophrenics have enlarged ventricles in their brains. Post-mortems have found that the brains of schizophrenics are lighter. This could reflect loss of cells in the brain.