What causes psychosis in veterans?

There are a number of theories about the cause or causes of psychosis. However, there is no single cause that is agreed upon or fits all cases. There seems to be a combination of biological, psychological and social factors involved in the development of psychosis in veterans and civilians. Genetics may play a role, as the disease is often seen in multiple generations or branches of families. Abnormalities in the function of brain messengers called neurotransmitters are believed to be involved. Substance abuse is sometimes cited, especially the use of marijuana or cannabis. Social stressors may trigger a psychotic break in people who are somehow predisposed to react hyper-sensitively to difficult life changes.