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Table 3 Comparison of clinical correlates between early onset bipolar disorder type 1 and type 2 patients

From: Clinical correlates of age at onset distribution in bipolar disorder: a comparison between diagnostic subgroups

Clinical variable

Early onset diagnostic subgroup

χ 2 or t

P

Bipolar disorder type 1 (N = 169)

Bipolar disorder type 2 (N = 142)

Female (%)

96 (56.8)

85 (59.9)

0.3

0.6

Age at interview, mean (SD)

45.3 (13.5)

42.8 (14.4)

1.5

0.01

Presence of family history of any psychiatric disorder (%)

99 (58.9)

93 (65.5)

1.4

0.2

Presence of family history of mood disorder (%)

85 (52.5)

84 (60.0)

1.7

0.2

Presence of family history of bipolar disorder (%)

31 (18.5)

36 (25.4)

2.2

0.1

Number of manic/hypomanic episodes, mean (SD)

4.4 (5.1)

4.3 (4.2)

0.2

0.8

Number of depressive episodes, mean (SD)

5.5 (4.7)

6.0 (5.6)

−0.8

0.4

Illness duration, mean (SD)

22.5 (12.8)

21.9 (13.7)

0.4

0.7

Lifetime comorbidity with substance dependence (%)

15 (8.9)

8 (5.6)

1.2

0.3

Lifetime comorbidity with alcohol dependence (%)

10 (5.9)

19 (13.4)

5.1

0.02

Presence of suicidal behaviour (%)

47 (28.0)

45 (31.7)

0.5

0.5

Type of clinical course cycle

 MDI (%)

75 (44.4)

51 (35.9)

10.4

0.035

 DMI (%)

20 (11.8)

31 (21.8)

 Irregular cycling (%)

65 (38.5)

58 (40.8)

 Continuous cycling (%)

5 (3.0)

2 (1.4)

 Rapid cycling (%)

4 (2.4)

0 (0.0)

  1. Significant values are typed in italics
  2. MDI (hypo)mania-depression-free interval, DMI depression-(hypo)mania-free interval, SD Standard Deviation, p p value