Family structure and risk factors for schizophrenia: case-sibling study

BMC Psychiatry

Table 4 Basic characteristics of sibships.

		no schizophrenia (%)		schizophrenia (%)		All
Sex	male	4636	47	5207	52	9843
	female	7410	66	3806	34	11216
Siblings under 5 years	no	5496	52	4876	48	10372
	yes	6550	61	4137	39	10687
Siblings 5–10 years	no	7727	52	7172	48	14899
	yes	4319	70	1841	30	6160
Siblings over 10 years	no	10094	55	8377	45	18471
	yes	1952	75	636	25	2588
Birth order	1	2934	44	3781	56	6715
	2	4297	57	3260	43	7557
	3	2629	68	1262	32	3891
	4+	2186	75	710	25	2896
Birth cohort	1950–1955	3756	51	3648	49	7404
	1956–1960	3566	57	2689	43	6255
	1961–1965	2825	62	1748	38	4573
	1966–1976	1899	67	928	33	2827
Maternal age	under 20	441	45	546	55	987
	20–25	2509	50	2462	50	4971
	26–30	3419	56	2692	44	6111
	31–35	2896	62	1778	38	4674
	over 35	2781	64	1535	36	4316
Paternal age	under 20	101	49	106	51	207
	20–25	1281	49	1355	51	2636
	26–30	2727	53	2413	47	5140
	31–35	2765	60	1879	40	4644
	over 35	4159	63	2407	37	6566
	not available	1013	54	853	46	1866
Sex of youngest proband	male	6880	57	5187	43	12067
	female	5166	57	3826	43	8992
Lowest age-at-onset in sibship	under 20	2797	54	2351	46	5148
	20–25	4410	57	3350	43	7760
	26–30	2930	59	2014	41	4944
	over 30	1909	60	1298	40	3207
Family size	2	3623	46	4233	54	7856
	3	3623	59	2551	41	6174
	4	2373	65	1284	35	3657
	5+	2427	72	945	28	3372
Mother schizophrenic	no	11537	57	8561	43	20098
	yes	509	53	452	47	961

ISSN: 1471-244X