Does psychomotor retardation define a clinically relevant phenotype of unipolar depression?

BACKGROUND: The recognition and assessment of psychomotor retardation may have implications for better definition of the clinical phenotypes of depression. The aim of this study was to assess the clinical correlates of psychomotor retardation endorsed at any time during the patients' lifetime (LPR). METHODS: The study sample included 291 patients with non-psychotic major depressive disorder (MDD) participating in the clinical trial, "Depression: The Search for Treatment-Relevant Phenotypes." Psychomotor retardation was measured using a factor derived from the Mood Spectrum Self-Report (MOODS-SR) assessment. Using a pre-defined cut-off score on the lifetime psychomotor retardation (LPR) factor of the MOODS-SR, participants were classified into high and low scorers. Logistic regression analysis was used to evaluate the relationship between LPR and subthreshold bipolarity. RESULTS: Compared to low scorers, participants with high scores on the LPR factor had greater severity of depression and more bipolarity indicators. CONCLUSIONS: The MOODS-SR appears to be helpful to identify clinical phenotypes of unipolar depression and to highlight the usefulness of a lifetime approach to the assessment of psychopathology in the characterisation of patients with unipolar depression.