Table 2.

Concordance rate table. Uncorrected concordance rates in schizophrenia twin studies from around the world and modeling results from fits to these data. Only significant studies published before 1970 are included here so that the updates of these studies could definitively test the predictions of the model.

Investigator	Year	Country	MZ pairs concordance	DZ pairs concordance	S inher*	P s(t,r)#	t, (r)
Rosanoff et al. [8]	1934	USA	28/41 = 0.683	15/101 = 0.149	0.190	0.812
Essen-M$\ddot{\text{o}}$ller[9]	1941	Sweden	6/11 = 0.545	4/27 = 0.148	0.224	0.706
Kallmann [10]	1946	USA	120/174 = 0.689	53/517 = 0.102	0.129	0.816	31.0 y, (1.94)
Slater [11]	1953	UK	24/37 = 0.648	10/112 = 0.0892	0.116	0.787
Inouye [12]	1961	Japan	33/55 = 0.600	2/17 = 0.117	0.163	0.750
Harvald and Hauge [13]	1965	Denmark	4/9 = 0.444	6/62 = 0.0967	0.167	0.615
Gottesman and Shields [14, 15]	1966	UK	10/24 = 0.416	3/33 = 0.0909	0.165	0.588	41.0 y, (1)
Kringlen [16]	1966	Norway	19/50 = 0.380	13/94 = 0.138	0.283	0.551
Hoffer and Pollin [17]	1970	USA	11/80 = 0.137	6/145 = 0.0413	0.197	0.242	43 y, (0.631)

*S _inher is defined as the probability that a fraternal cotwin of a schizophrenic will also inherit the susceptibility to develop schizophrenia.

^# P _s(t, r) is the prevalence obtained from a model simulation of twin study concordance results for a susceptible age cohort at age t.