Background:
This study aimed to identify and compare factors of a 31-item version of the HDRS (HDRS-31) in large samples of patients with bipolar and unipolar depression, then examine for any responsiveness of such factors to the anticonvulsant agent lamotrigine in the bipolar depressed sample.
Methods:
This multivariate analytical study was performed on two large depressed samples (one bipolar and the other unipolar) that had been recruited for separate double-blind placebo-controlled trials of la-motrigine. Both studies had very similar designs and assessment tools, the major measures being the MADRS and HDRS-31. To identify the constructs underlying the scale, exploratory factor analyses were applied to the HDRS-31. Treatment responsiveness in the bipolar depressed sample – as indicated by improvement in the total MADRS and HDRS-31, as well as any HDRS factors – was examined using both a mixed-effects analysis and individual time-point t-tests.
Results:
Seven factors of the HDRS-31 were identified: I – ‘depressive cognitions’, II – ‘psychomotor retardation’, III – ‘insomnia’, IV – ‘hypersomnia’, V – ‘appetite and weight change’, VI – ‘anxiety’ and VII – ‘anergia’. A significant therapeutic effect of lamotrigine in bipolar depression was found using the ‘depressive cognitions’ factor (from week 3) and ‘psychomotor retardation’ (from week 4).
Conclusions:
This study has identified seven factors of the HDRS in a large sample of patients with bipolar depression. It suggests that the major effect of lamotrig-ine in bipolar depression is primarily upon central depressive cognitions and psychomotor disturbance.
