Schizophreniform disorder is a mental disorder diagnosed when symptoms of schizophrenia are present for a significant portion of time (at least a month), but signs of disturbance are not present for the full six months required for the diagnosis of schizophrenia.

The symptoms of both disorders can include delusions, hallucinations, disorganized speech, disorganized or catatonic behavior, and social withdrawal. While impairment in social, occupational, or academic functioning is required for the diagnosis of schizophrenia, in schizophreniform disorder an individual's level of functioning may or may not be affected. While the onset of schizophrenia is often gradual over a number of months or years, the onset of schizophreniform disorder can be relatively rapid.

Like schizophrenia, schizophreniform disorder is often treated with antipsychotic medications, especially the atypicals, along with a variety of social supports (such as individual psychotherapy, family therapy, occupational therapy, etc.) designed to reduce the social and emotional impact of the illness. The prognosis varies depending upon the nature, severity, and duration of the symptoms, but about two-thirds of individuals diagnosed with schizophreniform disorder go on to develop schizophrenia.

Schizophreniform disorder is a type of mental illness that is characterized by psychosis and closely related to schizophrenia. Both schizophrenia and schizophreniform disorder, as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), have the same symptoms and essential features except for two differences: the level of functional impairment and the duration of symptoms. Impairment in social, occupational, or academic functioning is usually present in schizophrenia, particularly near the time of first diagnosis, but such impairment may or may not be present in schizophreniform disorder. In schizophreniform disorder, the symptoms (including prodromal, active, and residual phases) must last at least one month but not more than six months, while in schizophrenia the symptoms must be present for a minimum of six months.

The exact cause of the disorder remains unknown, and relatively few studies have focused exclusively on the etiology of schizophreniform disorder. Like other psychotic disorders, a diathesis–stress model has been proposed, suggesting that some individuals have an underlying multifactorial genetic vulnerability to the disorder that can be triggered by certain environmental factors. Schizophreniform disorder is more likely to occur in people with family members who have schizophrenia or bipolar disorder.

If the symptoms have persisted for at least one month, a provisional diagnosis of schizophreniform disorder can be made while waiting to see if recovery occurs. If the symptoms resolve within six months of onset, the provisional qualifier is removed from the diagnosis. However, if the symptoms persist for six months or more, the diagnosis of schizophreniform disorder must be revised. The diagnosis of brief psychotic disorder may be considered when the duration of symptoms is less than one month.

The main symptoms of both schizophreniform disorder and schizophrenia may include:

Various modalities of treatment, including pharmacotherapy, psychotherapy, and various other psychosocial and educational interventions, are used in the treatment of schizophreniform disorder. Pharmacotherapy is the most commonly used treatment modality as psychiatric medications can act quickly to both reduce the severity of symptoms and shorten their duration. The medications used are largely the same as those used to treat schizophrenia, with an atypical antipsychotic as the usual drug of choice. Patients who do not respond to the initial atypical antipsychotic may benefit from being switched to another atypical antipsychotic, the addition of a mood stabilizer such as lithium or an anticonvulsant, or being switched to a typical antipsychotic.