Chronic social isolation in the elderly may be related with diverse psychiatric disorders: chronic depressive episode, paranoia-type personality, and late non-schizophrenic psychosis.

In order to separate psychotic depression and non-schizophrenic psychosis with depressive mood, there is a need for more clearly defined criteria.

We report the case of a 68 yrs. women living alone at home for more than twenty years, with a complete social isolation for two years. This behaviour was found associated with severe delusion: she unreasonably felt persecuted by her flat's owner and she dissimulated an extensive basocellular carcinoma on her face threatening her life. A history of a short depressive episode at the time of her divorce was only found, as she demonstrated at initial assessment many paranoia personality traits. A review of literature on this disorders’ association was therefore undertaken.

Evolution after admission revealed the lack of effectiveness of antipsychotic treatment on delusion, but some efficiency of antidepressant. Nevertheless, personality traits remained unaffected by care. Literature on the association between mood disorders and non-schizophrenic psychosis is rare, and we suggest some criteria that may account for psychotic depression and be useful to treatment choice.

In the absence of a history of chronic mood or psychotic disorder, it is hypothesised that paranoia symptoms may account more for a psychotic depression than for late paranoid schizophrenia. This may have consequences for therapeutic strategy.