In the previous version of the DSM (the DSM-IV-TR), schizophrenia was divided into five subtypes: catatonic, disorganized, paranoid, undifferentiated, and residual. The purpose of defining these subcategories was to better predict what course a certain presentation of schizophrenia might take and what treatment options would be most effective. However, these subtypes have since been removed in the new DSM-5 (largely because their were not as useful as was hoped). Instead, schizophrenia is now understood as existing along a spectrum of psychotic disorders that include schizoaffective disorder, delusional disorder, and catatonia.

Schizophrenia

This self-portrait of a person with schizophrenia represents their perception of a distorted experience of reality.

Schizophrenia

Schizophrenia is a psychological disorder characterized by major disturbances in thought, perception, emotion, and behavior. In order to be diagnosed with schizophrenia, according to the DSM-5, a person must exhibit both a psychotic episode and two additional symptoms for most of one month, and their symptoms must have a significant impact on social or occupational functioning for at least six months. The "two additional symptoms" can be delusions, hallucinations, disorganized speech, or a negative symptom or severely disorganized or catatonic behavior. If delusions or hallucinations or severe, only one symptom may be sufficient for diagnosis.

Schizoaffective Disorder

Schizoaffective disorder is characterized by abnormal thought processes and dysregulated emotions. A person with this disorder has features of both schizophrenia and a mood disorder (either bipolar disorder or depression) but does not strictly meet the diagnostic criteria for either. The bipolar subtype is distinguished by symptoms of mania, hypomania, or mixed episodes; the depressive subtype is distinguished by symptoms of depression only. Common symptoms of schizoaffective disorder include hallucinations, paranoid delusions, and disorganized speech and thinking.

The DSM-5 distinguishes schizoaffective disorder from psychotic depression or psychotic bipolar disorder by additionally requiring that a psychotic condition must last for at least two continuous weeks without mood symptoms (although a person may be mildly depressed during this time). Two episodes of psychosis (an increase from one episode in the DSM-IV) must be experienced in order for the person to qualify for this diagnosis.

Delusional Disorder

Delusional disorder is a psychiatric condition in which the person presents with delusions but no accompanying hallucinations, thought disorder, mood disorder, or significant flattening of affect. Apart from their delusions, people with delusional disorder may continue to socialize and function normally; their behavior does not stand out as odd or bizarre. However, their preoccupation with delusional ideas can disrupt their lives.

There are 7 subtypes of delusional disorder: 

1. Erotomanic type (erotomania): Delusion that another person, often a prominent public figure, is in love with the individual.
2. Grandiose type: Delusion of inflated worth, power, knowledge, or identity.
3. Jealous type: Delusion that the individual's sexual partner is unfaithful when such is not the case.
4. Persecutory type: Delusion that the person (or someone the person is close to) is being treated badly or malevolently.
5. Somatic type: Delusion that the person has some physical defect or medical condition.
6. Mixed type: Delusions with characteristics of more than one of the above types but with no single predominant theme.
7. Unspecified type: Delusions that cannot be clearly classified into any of the subcategories.

To be diagnosed with a delusional disorder, the individual's delusions must last for at least one month and cannot be due to the effects of a drug, medication, or general medical condition. Delusional disorder cannot be diagnosed in an individual previously correctly diagnosed with schizophrenia. Auditory and visual hallucinations cannot be prominent, though olfactory or tactile hallucinations related to the content of the delusion may be present.

Catatonia

Broadly speaking, catatonia is any condition of abnormal motor activity thought to be caused by a psychiatric disorder. For example, individuals with schizophrenia can demonstrate manic patterns of repetitious movement with no purpose, compulsively mimic the sounds or movements of others, or maintain the same posture for a long period of time without moving. In the DSM-5, catatonia is not recognized as its own disorder but rather is listed as a symptom of other psychiatric conditions, such as schizophrenia, bipolar disorder, post-traumatic stress disorder, and depression.