Table 1.

Demographic and Clinical characteristics US- and Dutch sample.

	US sample		Dutch sample		P
	N	%	n	%
Offspring
Bipolar offspring	224	100	136	100
Mean age, sd	13.51	2.3	14.12	2.2	.02
Sex, girls	113	50.4	66	48.5	.72
Living with both biological parents	92	41.1	100	73.5	<.001
Caucasian	187	83.5	121	89.0	.15
Family
Families	159	100	93	100
Employment	105	66.0	83	89.2	<.001
Bipolar parent
Sex, female	124	78.0	55	59.1	.001
Bipolar I disorder	107	67.3	75	80.6	.02
Substance use disorder	104	65.4	14	15.1	<.001
Age of BD onset:
− < 19	80	50.3	24	25.8	<.001
− 19–25	41	25.8	31	33.3
− >25	33	20.8	38	40.9
Biological co-parent
Mood disorder	37	23.3	16	17.2	.06
Substance use disorder	43	27.0	3	3.2	<.001
Mania	2	1.6	1	1.1	1.00
Psychosis	0	0	1	1.1	.423
Source of recruitment					<.001
- Advertisement	101	63.5	4	4.3
- Psychiatric clinics	58	36.5	35	37.6
- Patient advocacy groups	0	0	54	56.1
Informant Categorical psychopathology, K-SADS-PL
Single informanta	224	100	78	57.4	<.001
Motherb	197	88.7	128	94.1	.08
Bipolar parent	168	75.7	102	75.0	.89
Dimensional psychopathology, CBCLc
Motherc	169	79.0	75	67.0	.02
Bipolar parent	214	95.5	112	82.3	.01

^aOne informant versus both parents.

^bMother versus father or significant other (n = 7).

^cAs the majority of CBCLs were completed by the bipolar proband; only CBCLs completed by the bipolar proband were selected for further analyses. In total, nine subjects in the US sample and one subject in the Dutch sample had a missing value rate over 5% and were excluded from the analyses.