Table 2.

Sociodemographic and clinical characteristics in primary BD and secondary BD

	Primary BD	Secondary BD	Statistics
	N = 117	N = 34
Age, y, mean (SD)	36.50 (12.2)	33.7 (10.4)	t = 1.2, df = 149, P = 0.227a
AAO, y, mean (SD)	21.8 (9.0)	25.9 (9.8)	t = −2.3, df = 149, P = 0.020 a
Age at onset of excessive substance use, y, mean (SD)*	27.0 (11.6)	20.1 (7.0)	t = 2.9, df = 64, P = 0.005 a
Gender, female, n (%)	74 (63.2)	18 (52.9)	χ² = 1.2, df = 1, P = 0.278b
Type I BD, (%)	68 (58.1)	23 (67.6)	χ² = 1.0, df = 1, P = 0.318b
Family history of affective/psychotic disorder, n(%)	45 (39)	17 (52)	χ² = 1.6, df = 1, P = 0.204b

Significant P-values are typed in bold

BD Bipolar disorder, AAO Age at onset of BD, y Years

* For the 32 patients with excessive substance use in the primary BD group

^aStudent’s t-test

^bChi-square test