Original articleRisk of conversion to bipolar disorder in patients with late-onset major depressionElefante, Camillaa; Brancati, Giulio Emilioa; Petrucci, Alessandraa; Gemmellaro, Teresab; Toni, Cristinac; Lattanzi, Lorenzod; Perugi, Giulioa,c Author Information aDepartment of Clinical and Experimental Medicine, University of Pisa, Pisa bDepartment of Psychiatry, North-Western Tuscany Region, NHS Local Health Unit, Viareggio cInstitute of Behavioral Science “G. De Lisio” dAzienda Ospedaliero-Universitaria Pisana, Pisa, Italy Received 2 May 2022 Accepted 13 June 2022 Correspondence to Giulio Perugi, Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56100, Pisa, Italy, Tel: +39 050 992965; fax: +39 050 2219775; e-mail: [email protected] International Clinical Psychopharmacology: July 22, 2022 - Volume - Issue - 10.1097/YIC.0000000000000421 doi: 10.1097/YIC.0000000000000421 Buy PAP Metrics Abstract To evaluate the impact of age at onset on late-life depression course and on risk of conversion to bipolar disorder (BD). A retrospective chart review of 100 elderly patients (age ≥ 65 years) diagnosed with a moderate-to-severe depressive episode and followed up for at least 18 months was conducted. Among patients affected by major depressive disorder (N = 57), follow-up morbidity differences between those with typical onset depression (TOD) (<60 years) and those with late-onset depression (LOD) (≥60 years) were investigated using Wilcoxon rank-sum test and Cox proportional hazard model. Patients belonging to the LOD group had a significantly lower percentage of follow-up time spent with depressive symptoms compared with patients with TOD (r = 0.36; P = 0.006), but significantly more time spent with (hypo)manic episodes (r = −0.31; P = 0.021). Moreover, LOD was significantly associated with a faster conversion to BD (hazard ratio = 3.05; P = 0.037). Depression first emerging in late life may represent an unstable condition with a high risk to convert to BD. Given the potential clinical implications, further studies on the course of LOD are required. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.