Delusional disorder: the predictive validity of the concept.

A sample of 72 first-admitted patients with delusional disorder was personally re-examined after a mean of 10 years, and 42 of them after an average of 27 years. The mean observation period for all patients from admission to last follow-up was 20 years (3-39). There was a trend that patients with delusions of jealousy did better on course variables, but similar outcomes were revealed in groups with delusions of jealousy, persecution and a mixed group with different main delusions. Duration of symptoms prior to admission was a significant predictor of outcome, indicating dividing lines of 1 and 6 months at 10-year follow-up and 3 and 6 months at long-term follow-up. Based on the data, a minimal duration of 6 months is proposed for persistent delusional disorder.