A factor analytic study in bipolar depression, and response to lamotrigine.
Author(s): Mitchell PB(1), Hadzi-Pavlovic D, Evoniuk G, Calabrese JR, Bowden CL.
Affiliation(s): Author information:
(1)1 School of Psychiatry, University of New South Wales, Sydney, Australia.
Publication date & source: 2013, CNS Spectr. , 18(4):214-24
OBJECTIVE: There have been no previous factor analytic studies of the Hamilton
Depression Rating Scale (HDRS) in samples with bipolar I depression, and no
investigations of the utility of any derived factors in determining treatment
response in this condition. 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
depression and Major Depressive Disorder (MDD), then examine the responsiveness
of such factors to lamotrigine compared with placebo in the bipolar depressed
sample.
METHODS: This multivariate analytical study was performed on 2 large depressed
samples (one bipolar and the other MDD) that had been recruited for separate,
contemporaneous, double-blind placebo-controlled trials of lamotrigine. The 2
studies had similar designs and assessment tools, the major measures being the
Montgomery-Asberg Depression Rating Scale (MADRS) and HDRS-31. To identify the
constructs underlying the scale, exploratory factor analyses were conducted using
HDRS-31 baseline scores. Treatment responsiveness in the bipolar depressed
sample-as indicated by improvement in the total MADRS and HDRS-31, as well as
HDRS factors-were 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 for the "depressive cognitions"
factor (from week 3) and "psychomotor retardation" (from week 4).
CONCLUSION: This study has identified 7 factors of the HDRS in a large sample of
patients with bipolar depression. The results suggest that that the clinical
benefits of lamotrigine in acute bipolar depression are primarily upon depressive
cognitions and psychomotor slowing.
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