Ann Hum Genet. 1994 Oct;58(Pt 4):321-9.
Tunçbílek E, Koc I.
Hacettepe University Institute of Population Studies, Ankara, Turkey.
Turkey has a high rate of consanguineous marriage (21.1%), indicating strong preference for this traditional form of marital union. Social and cultural factors are especially important in marriages between first and second cousins. Fertility is high, the closed birth interval is long, and the sterility rate is low among these couples. Post-neonatal, infant and under-5 mortalities are high in first cousin unions by comparison with non-consanguineous marriages. According to the results of the study, first cousin marriage is a significant determinant underlying the high total fertility and infant mortality rates in Turkey.
Sly Turks of the Kemalist variety will blame this high rate of inbreeding on Kurds, but even the Turks of Western Turkey or "white Turks", have a high rate of consanguinity:
1999, Vol. 26, No. 5 , Pages 489-491 (doi:10.1080/030144699282598)
M. TURE, B. TUGRUL, N. MERCAN, H. TURE, B. AKDAG
For the study 1000 families were interviewed during 1996 in the city of Denizli, which is situated in Western Anatolia and has a population of 79 211 families. The overall rate of consanguinity was 11.7% ... The principal type of consanguineous marriage recorded was between first cousins, which accounted for 49.6% of all unions. For both sexes, a significant negative association was observed between consanguinity and mean age at marriage and level of education.
But the rate is higher in Eastern Turkey:
The frequency of consanguineous marriage in eastern Turkey.
Akbayram S, Sari N, Akgün C, Doğan M, Tuncer O, Caksen H, Oner AF
Department of Pediatrics, Yüzüncü Yil University Faculty of Medicine, Van, Turkey.
Genetic Counseling (Geneva, Switzerland) [2009, 20(3):207-214]
METHODS: This study was performed in Van region, Eastern Turkey, between September 2005 and April 2006. A total of 650 families from 24 districts chosen in accordance with the number of inhabitants were included in this study. First cousin marriages were accepted as a first degree CMs, sesquialter and second cousin marriages as second degree and marriages between distant relatives were accepted as a third degree CM. ...
RESULTS: Of all families, 224 (34.4%) had CM, and 168 (75%) had first-degree consanguinity. A lower CM rate was found in mothers who graduated from secondary school or upgrading (p < 0.01). However, no relationship was found between CM and fathers' education level. While a low CM rate was found in families who had two or less children (p < 0.01), high rate was observed in families who had five or more children. In addition, a high rate of miscarriage, stillbirth and mental-motor retardation was found in families with CM (p < 0.05). The rate of child mortality between the aged 0-2 years was found to be higher in families with CM (p < 0.01). The higher CM rate was observed in families who married due to pressure or insistence of their families than married voluntarily (p < 0.05).
According to another study, even on the Mediterranean coast of Turkey, inbreeding is increasing amongst the rural populace, not decreasing.