Latent Bipolarity In Unipolar Depression: Experimental Findings, Conceptual Analysis And Implications For Treatment Strategies

Abstract Introduction: Previous studies have suggested that the two opposite poles of psychomotor disturbances in unipolar depression (UD) – retardation and agitation – require different treatment strategies as the psychomotor overactivation requires an augmentation of the antidepressant therapy with mood stabilizers and/or atypical antipsychotics. Objective: The aim of the present study was to objectively identify and measure the psycho-motor disturbances in UD using differentiation between activity and reactivity. Material and methods: An equilibriometric movement pattern analysis system that allows differentiation between psychomotor activity and reactivity was applied in 58 unipolar depressive patients and 76 healthy controls. Results: Compared to controls, the patients as a group were significantly slower in their psychomotor reactivity. However, the subsequent subgrouping according to the direction of deviation of their objective psychomotor parameters revealed a disinhibition of psychomotor activity and/or reactivity in about one half of them. Such a contradictory combination of clinically manifested depressive mood and subclinically detected manic-like psychomotor overactivation might be regarded as belonging to the bipolar spectrum, since it was admitted that manic psychomotor disinhibition in unipolar depressive patients uncovers a latent bipolarity. Conclusion: Not only prototypical depressive inhibition, but also prototypical manic-like disinhibition may underlie clinically manifested UD. Since the combination between depressive mood and psychomotor overactivation multiplies the suicidal risk, we may presume that the timely detection of this combination at a subclinical level would contribute to an earlier and more effective suicidal prevention by an objectively-guided optimization of pharmacological treatment.