Psychosis is a loss of contact with reality. Psychosis often involves delusions and seeing or hearing things that others can not see or hear (hallucinations.) People with psychosis often feel fearfulness or suspiciousness (paranoid). Psychosis may develop suddenly or gradually. Psychosis may occur as part of other mental health disorders. Some people with depression develop psychosis and some older people with dementia have psychosis. Drugs called anti psychotic can be effective in reducing the symptoms of psychosis.