There are several different theories that can explain schizophrenia. There are biological explanations such as the dopamine hypothesis and genetic explanation, and there are social explanations such as the role of environmental factors. The genetic explanation suggests that schizophrenia is hereditary and is caused by genes. Studies of monozygotic and dizygotic twins in the 1950s often supported this theory. However, more recent studies tend not to support this claim. Another biological explanation is the dopamine hypothesis, which suggests that hyperactivity of dopamine, a neurotransmitter in the brain, causes schizophrenia. Social theories suggest that environmental factors such as trauma, low socio-economic status and inequality (to name a few), cause schizophrenia. However, recently studies have suggested that there is an interaction between biological and social factors. An individual may have a biological disposition to schizophrenia, but it may only be triggered if certain environmental factors occur. Equally, an individual may be subject to certain environmental factors, but they will not develop the disorder as they do not have a biological predisposition to it.