In which disorder does the individual return to full premorbid functioning after experiencing symptoms for less than one month?

The disorder characterized by the individual returning to their full premorbid functioning after experiencing symptoms for less than one month is brief psychotic disorder. Brief psychotic disorder is defined by the sudden onset of psychotic symptoms, which may include hallucinations, delusions, disorganized speech, or catatonic behavior, and these symptoms typically last for more than a day but less than one month. Following the episode, individuals fully recover, returning to their previous level of functioning without lingering effects.

In contrast, other disorders listed involve either longer durations of symptoms or different recovery trajectories. For example, delusional disorder involves persistent delusions that can last for months to years without the same level of return to premorbid functioning. Schizophreniform disorder represents a longer duration of psychotic symptoms, ranging from one month to six months, and does not guarantee a complete return to premorbid functioning upon resolution. Tardive dyskinesia, however, refers to a movement disorder caused by long-term use of antipsychotic medications and is not classified as a psychotic disorder to begin with. Thus, brief psychotic disorder is distinctly identified by its shorter duration and full recovery aspect.