Which disorder requires at least one month of active-phase symptoms?

Schizophreniform Disorder is characterized by the presence of at least one month of active-phase symptoms, which may include delusions, hallucinations, disorganized speech, and disorganized or catatonic behavior. This disorder lasts for a minimum of one month but less than six months, which distinguishes it from Schizophrenia, where symptoms must persist for at least six months.

The emphasis on the one-month duration for active-phase symptoms is essential because it highlights the point at which a diagnosis can be made, differentiating Schizophreniform Disorder from other disorders that might present with psychotic symptoms.

Delusional Disorder, on the other hand, involves the presence of one or more delusions lasting one month or longer but does not require the full constellation of active-phase psychotic symptoms. Brief Psychotic Disorder requires symptoms that last for at least one day but less than one month. Neuroleptic Malignant Syndrome, while a serious condition, is not classified as a mental disorder in the DSM-5 and does not involve the same symptoms or diagnostic criteria as the psychotic disorders mentioned.

Therefore, the requirement of at least one month of active-phase symptoms is unique to Schizophreniform Disorder among the options provided.