schizophrenia is a mental disorder characterised by a breakdown of thought processes and by poor emotional responsiveness. it most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganised speech and thinking, and it is accompanied by significant social or occupational dysfunction. the disorder is thought mainly to affect cognition, but it also usually contributes to chronic problems with behaviour and emotion. people with schizophrenia are likely to have additional (comorbid) conditions, including major depression and anxiety disorders; the lifetime occurrence of substance abuse is almost 50%. social problems, such as long-term unemployment, poverty and homelessness, are common. the average life expectancy of people with the disorder is 12 to 15 years less than those without, the result of increased physical health problems and a higher suicide rate (about 5%).