Children born to consanguineous parents more likely to have poor mental health
Children of consanguineous parents appear to be at a higher risk of common mood disorders and psychosis, a recent Ireland study has shown.
Linking a national birth data set and a nationwide data source on prescription medication and death records, researchers evaluated the degree of parental consanguinity in 363,960 individuals (52.5 percent male) through routine phone calls. Receipt of antidepressant and antipsychotic medications were used as proxy indicators for common mood disorders and psychoses.
Only a small proportion of the participants had consanguineous parents (0.2 percent; n=609), of whom 349 were born to second cousins while 260 were born to first cousins. A higher percentage of children of consanguineous vs nonrelated unions received antidepressant or anxiolytic medications (35.8 percent vs 26.0 percent). A similar trend of use was observed for antipsychotic medication in second-cousin vs unrelated unions (4.3 percent vs 2.7 percent). [JAMA Psychiatry 2018;doi:10.1001/jamapsychiatry.2018.0133]
Fully adjusted analyses showed that children of first cousins were more than three times as likely to receive medication for common mood disorders (odds ratio [OR], 3.01; 95 percent CI, 1.24–7.31) and more than twice as likely to receive antipsychotics (OR, 2.13; 1.29–3.51) compared with children of nonrelated parents.
A similar, nominal positive association was observed for children born to second-cousin consanguineous parents, but did not react statistical significance: common mood disorder (OR, 1.31; 0.63–2.71) and psychotropic medications (OR, 1.37; 0.79–2.40). All associations were robust to singleton birth-specific analyses.
“The results illustrate a clear increasing, stepwise association between level of consanguinity and mental [illness], suggesting a quasi–dose-response association, supporting a causal association between consanguineous parents and mental health of progeny,” said researchers.
There are several potential explanations for this association. One focuses on the genetic component of psychiatric disorders. In recent years, genome-wide association studies have shown that many small genetic effects collectively contribute to various conditions such as major depression and bipolar disorder. [Biol Psychiatry 2017;81:325-335]
“As a form of assortative mating, consanguinity increases polygenic loading and thus is likely associated with a higher risk of mental disorder in progeny,” researchers explained, however noting that this holds only if both parents have common susceptibility loci. [Nat Genet 2006;38:1224-1225]
Another theory deals with the social stigma of having consanguineous parents, which is considered highly unusual particularly in Western societies. [J Genet Couns 2002;11:97-119]
“We suggest that these findings will be of value to health promotion and public health professionals and to those commissioning antenatal, paediatric and clinical genetic services,” said researchers.
“Sensitive advice about the risks should be provided to communities that favour consanguineous unions to assist in reproductive decision-making,” they added.