To Örebro University

Aims: The aims of this thesis were to summarize and extend current knowledge on maintenance treatment in psychotic depression and to examine diagnostic conversion rates from psychotic unipolar depression to bipolar disorder and psychotic disorders.

Methods: Study I was a systematic review, and Studies II–IV were nationwide observational studies based on Swedish national registers.

Results: The systematic review included five controlled studies. Only the comparison between antidepressant–antipsychotic combination therapy and antidepressant monotherapy had been assessed in more than one study, and a meta-analysis of this comparison did not show a significant difference. In Swedish register data, antidepressant monotherapy was associated with a lower risk of rehospitalization or suicide compared with antidepressant–antipsychotic combination therapy. Maintenance treatment with electroconvulsive therapy (ECT) was not associated with a decreased risk of rehospitalization or suicide in patients overall; however, a significant association in favor of maintenance ECT was found among patients aged over 65 years. In patients with psychotic unipolar depression, 17-year conversion rates were 17.5% to psychotic disorders and 14.7% to bipolar disorder.

Conclusions: Evidence for adjunctive antipsychotics in the maintenance phase is limited, and they should be used with caution. Maintenance ECT may lower relapse risk in patients over 65 years. Diagnostic conversion to psychotic and bipolar disorders is common, which may have important implications for treatment and prognosis.The epidemiology and treatment of psychotic depression remain understudied, warranting further research.