In addition, 8 subjects had mental disorder other than bipolar disorder, and they were excluded from subsequent analysis.Table 1The study sample of bipolar disorder twins and co-twins.There was a greater proportion of men among the bipolar than healthy twins (F [1,37] = 4.75, p = 0.04), but there was no difference in the affection status by zygosity.Seasonal variation in hospital admissionTwins wi