The use of combined mood scores in studying the premenstrual syndrome: does it clarify or muddy the picture?
Forty-four women with premenstrual syndrome kept a daily record of seven moods for two to four menstrual cycles. Principal components analysis of the mood scores for each woman showed a clear main component accounting for much of the variance (mean = 75%). Only in two cases was there evidence of a very minor second component. These results indicate that, for these moods, a single mood sum is a suitable measure to use when looking for premenstrual change. Inspection of simultaneous time plots, means and standard deviations supported the conclusion from the principal components analysis. Metcalf et al.' found the same pattern for all seven moods when they aggregated data across women. The present study shows that for individual women the moods rise and fall together so that the pattern found with aggregated data does reflect the pattern for individual women.
Wells
J E
JE
Department of Community Medicine and General Practice, Christchurch School of Medicine, P O Box 4345, Christchurch.
Metcalf
M G
MG
Livesey
J H
JH