Think of your genes, shun cousin marriages
Several other studies suggest that between the 1980s and the 2000s the rate of cousin marriage has increased in several Gulf nations.
The link between parental consanguinity (marriage between relatives, typically cousins) and the increased incidences of autosomal recessive genetic disorders, thalassemia, for example, is well established. The links with mental health problems, however, are less clear.
Consanguineous marriage (zawaaj al aqaarib in Arabic) is relatively common across the Gulf states. In a study of 72 nations, very few countries (Kyrgyzstan, Tajikistan, Afghanistan, Pakistan, Sudan, Nigeria and Burkina Faso) had consanguineous marriage (cousin marriage) rates higher than those reported within the Gulf states. With a high of 54.5 per cent for Qatar and a relative low of 35.9 per cent for Oman, consanguineous marriage remains a popular option. Popular in the numeric sense at least.
Several other studies suggest that between the 1980s and the 2000s the rate of cousin marriage has increased in several Gulf nations. The reasons for why this practice persists, and perhaps thrives, remain highly speculative. A common misconception is that Islam advocates it. Cousin marriage is permitted, but not actively encouraged. The founder of one dominant school of Islamic thought - Imam Al Shafi - actively discourages it. "It is recommended that one not marry from amongst his near relatives."
One suggestion for the persistence and apparent increase in cousin marriage is that it promotes family unity and concentrates family wealth. With more wealth around, perhaps the marital net is now cast less widely. Another observation is that consanguineous marriage appears to increase among social groups when the group becomes a minority within the general population. With more expatriates around, perhaps the marital net is now cast less widely.
Whatever the reasons behind cousin marriage - cultural, economic, demographic - there are potential health implications for the offspring. It should be said that these implications could be negative or positive. If you can inherit a genetic vulnerability/risk, you can also inherit genetic resilience. Most research, however, focuses on genetic risk, and the risk for mental health problems has also received some attention in recent years.
Studies in Egypt report an increased risk for bipolar disorder among the children of consanguineous/cousin marriages. One study, published in the American Journal of Medical Genetics, looked at the parents of 93 bipolar patients compared to 90 healthy controls. Parental consanguinity (both parents being first cousins) was established through self-report and DNA testing. The study found that individuals diagnosed with bipolar disorder were almost three times more likely to be the children of cousin marriages.
This Egyptian study is not conclusive evidence of a genetic link and an increased risk caused by consanguineous marriage. It is possible that among Egyptians, people who opt to marry their cousins differ in other meaningful ways too, such as socioeconomic status or lifestyle. Both of which might better explain the elevated rate of bipolar disorder among their children. Further research is required to identify any causal genetic link between cousin marriage and an increased risk for bipolar disorder.
Another more obvious mental health implication of cousin marriage, though, has to be the stress associated with pre-marital screening. Similarly, there is also all the stress related to the uncertainty of not knowing for sure if your child will be affected by an autosomal recessive genetic disorder. Finally, there is the stress, and perhaps a misplaced sense of guilt, related to caring for a child with such a disease or disorder. We certainly need more research into how best to support people at each stage of this journey, psychologically. We then need to act on that knowledge by providing culturally appropriate, evidence-based psycho-educational interventions.
Justin Thomas is Associate Professor at the College of Natural and Health Sciences, Zayed University, Dubai