Psychosis can occur in individuals due to a variety of reasons. Substance abuse can lead to experiencing psychotic symptoms such as paranoia, delusions, and hallucinations. There are some mental health disorders that are diagnosed due to symptoms such as paranoia, delusions, and hallucinations (among others). Sometimes a person may hear voices, see people or things, or even feel something that someone else would not. An individual may experience a psychotic episode that may be short or long in duration. Therapy is beneficial in addressing these symptoms as well as disorders that are classified by these symptoms.