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Criminal behavior, substance abuse linked to genetic factors in children of triparental families

Children in triparental families consisting of a mother, a stepfather and a biological father living outside the home are more likely to participate in criminal behavior, drug abuse or alcohol use if their biological parents also engaged in these activities, according to recently published data.

“For drug abuse, alcohol use disorders, and criminal behavior, the results of this study suggest that parent-offspring transmission involves both genetic and environmental processes, with genetic factors being somewhat more important,” Kenneth S. Kendler, MD, director at the Virginia Institute of Psychiatric and Behavioral Genetics, and colleagues wrote.

The researchers used a national Swedish registry to identify 41,360 people born between 1960 and 1990 who were raised in a household with their biological mother and stepfather, while their biological father lived outside the home.

They found the HR for drug abuse for these children was highest for mothers at 2.8 (95% CI, 2.23-3.38), intermediate for biological fathers living outside the home at 2.45 (95% CI, 2.14-2.79), and lowest for stepfathers at 1.99 (95% CI, 1.55-2.56), according to the abstract.

When analyzing alcohol use and criminal behavior, the researchers found the same pattern of cross-generational transmission; however, the risk for parent-offspring transmission was different significantly among all groups. Mothers carried the highest risk of passing on alcohol use disorders to their children (HR = 2.23, 95% CI, 1.93-2.58), followed by biological fathers living outside the home (HR = 1.84, 95% CI, 1.69-2) and stepfathers (HR = 1.27, 95% CI, 1.12-1.43). Criminal behavior was not statistically significant when comparing mothers (HR = 1.55, 95% CI 1.44-1.66) and biological fathers living outside the home (HR = 1.46, 95% CI 1.40-1.52).

The researchers examined all three factors together and found that mothers had the highest rate of cross-generational transmission, fathers living outside the home had an intermediate rate, and stepfathers had the lowest rate.

“Analyses of intact families and other not-lived-with parents and stepparents showed similar cross-generation transmission for these syndromes in mothers and fathers, supporting the representativeness of results from triparental families,” Kendler and colleagues wrote. – by Jeffrey Craven