No single cause has been identified, biological, behavioural and social research suggests a complex interplay between factors. For example, people might have an inherited tendency towards schizophrenia that is triggered by environmental circumstances.
Family history studies show that schizophrenia tends to run in families.
The rate of schizophrenia in the general population is about 1%, but estimates vary.
Studies using twins show that in identical (monozygotic or MZ) twins, if one has schizophrenia, the other has 40-50% chance of developing the illness.
Concordance rates for schizophrenia are three times higher in identical twins than non-identical twins (dizygotic or DZ).
If one parent has schizophrenia then a child has about ten percent chance of developing it.
The problem with families, including twins, is that they share the same environment.
The search for genes that may contribute to schizophrenia has indicated that chromosomes number 6 and 13 might be involved, but evidence so far is uncertain.
Genetic factors could be behind biochemical or neurological defects outlined below.
The main biochemical explanation for schizophrenia is the dopamine hypothesis. This idea is based on the role of chemical messengers between nerve cells called neurotransmitters. There seems to be a chemical imbalance in the action of the neurotransmitter dopamine in the brains of those with schizophrenia.
Evidence for the dopamine hypothesis:.
Drugs: Antipsychotic or neuroleptic drugs are known to dampen the effects of dopamine, by blocking dopamine receptors. These help to relieve symptoms of hallucinations and delusions in many sufferers.