Israel is all-too-aware of the genetic price of inbreeding. The entire Ashkenazi (European Jewish) population alive today is believed to have descended from a tiny group of just 350 people who lived 600 to 800 years ago. Ashkenazim today are associated with no less than 19 genetic and mental disorders.
Haaretz
Children of cousins who marry are significantly more likely to suffer from psychosis, depression and/or anxiety, a vast Irish study has found. The results were reported Wednesday in JAMA Psychiatry.
There’s a reason that both religion and civil law tend to steer people away from consanguinity, meaning, marriage between related people. There’s a satirical Facebook community page in Hebrew called ‘When Daddy and Mommy are Cousins,’ and it isn’t about granny’s cooking tips. Users upload links to news reports about stupid or mind-boggling things people do, such as the woman seeking advice about a cheating ex, or the four British men who joined ISIS complaining about England stripping them of their citizenship because that could expose them to brutality.
The inference isn’t that consanguinity induces identification with ISIS. It’s that procreating with family increases the probability that negative recessive traits lurking in the family will be expressed. The Irish study sought to clarify whether children born to first cousins are at heightened risk of psychosis and/or mood disorders too, and found that they very much are.
First-cousin marriages are perfectly legal in Europe and most of the United States. Cousin marriages do statistically have more birth defects among their progeny than do unrelated couples, though it bears qualifying that the problem of ‘kissing cousins’ is less acute when the couples are the first in the family to do so. The trouble chiefly arises when cousin-cousin marriage is the norm in the family or society.
Recessive traits accrue, as demonstrated by an Egyptian study dating from 2013, which described how ‘stillbirths, child deaths and recurrent miscarriages were significantly increased among consanguineous parents’ compared with non-related parents.
The Irish paper reported in JAMA, ‘Consanguineous Marriage and the Psychopathology of Progeny,’ looked at well over a quarter-million people – specifically, 363,960 people born in Northern Ireland from 1971 to 1986; nationwide data on prescription medication; and deaths records.
The relationship between the parents was ascertained by asking them.
Psychosis was ‘identified’ by receipt of antipsychotic medications; mood disorders were ‘identified’ by receipt of antidepressant or anti-anxiety drugs.
All in the family genetics
The result is not a happy one. After full adjustment for factors known to be associated with poor mental health, the researchers in the Irish study calculated that children of first-cousin consanguineous parents were more than 3 times as likely to be prescribed antidepressant or anxiolytic medications. They were more than twice as likely to be in receipt of antipsychotic medication compared with children of non-related parents.
So the probability of mental difficulties has to be added to the probability of physical ones.
The most startling statistic in the 2013 Egyptian study was that almost 93% of the children born with limb abnormalities turned out to have related parents. Its conclusion was that public health education and genetic counseling are highly recommended in the community.
Israel is all too versed in the genetic price of inbreeding. The entire Ashkenazi (European Jewish) population alive today is believed to have descended from a tiny group of just 350 people, roughly speaking, who lived 600 to 800 years ago. The bottleneck occurred 25 to 30 generations ago, according to the Columbia University study – and Ashkenazim today are associated with no less than 19 genetic disorders.
Marriage within the Ashkenazi community isn’t as high-risk as marrying a first or even second cousin, but before the rabbi sings the nuptial blessings, Ashkenazi Israelis typically undergo genetic testing for at least some inheritable diseases, such as the deadly Tay-Sachs.
