Children born of first-cousin consanguineous parents are at greater risk for common mood disorders and psychoses, according to the results of a study published in JAMA Psychiatry.
Consanguinity is defined as a marriage between individuals who are second cousins or closer. Worldwide, about 1 in 10 children are born of a consanguineous marriage. Children born of first-cousin marriage are homozygous at one-sixteenth of all loci, which is thought to lead to the higher incidence of autosomal-recessive disorders seen in these children.
Aideen Maguire, PhD, of the Centre for Public Health at Queen’s University Belfast in Belfast, United Kingdom, and colleagues conducted a retrospective population-wide cohort study of all individuals born in Northern Ireland between January 1, 1971, and December 31, 1986, derived from the Child Health System data set and linked to nationwide administrative data sources on prescription medication and death records. The investigators identified 447,452 births, with a final data set comprised of 363,960 individuals with full data available on all relevant variables. They analyzed the data between June 1, 2017 and October 31, 2017.
The investigators used records of health visitor house calls that assessed parental relatedness within 2 weeks of a child’s birth to determine the degree of consanguinity, and they estimated potential mental illness using records of psychotropic prescriptions between 2010 and 2014. They employed ever or never use for the main analysis and a cut-off of at least 3 months’ prescriptions for the sensitivity analyses. Receipt of antidepressants or anxiolytics served as a proxy for common mood disorders, and antipsychotic medications functioned as a proxy for psychoses.
The investigators found that 609 individuals (0.2%) were born to consanguineous parents. After adjusting for factors associated with poor mental health, multilevel logistic regression models determined that children of first-cousin consanguineous parents were 3 times more likely to be prescribed antidepressants or anxiolytics (odds ratio 3.01) and more than twice as likely to receive antipsychotic medication (odds ratio 2.13) compared with children born to nonrelated parents.
The study limitations include the use of prescription medication receipt as a proxy for mental illness rather than diagnoses, that consanguinity was determined by self-report, and that there is no information on parental mental health.
The authors suggest that communities that favor consanguineous marriage should receive sensitive advice on the risks involved to aid in reproductive decision making.
Maguire A, Tseliou F, O’Reilly D. Consanguineous marriage and the psychopathology of progeny.: a population-wide data linkage study [published online April 4, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.0133