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Genetic effects on irritability increase with age among males, not females

The genetic effects on irritability increase as adolescent males age, but they decrease with age among adolescent females, according to study findings in the American Journal of Psychiatry.

Roxann Roberson-Nay, PhD, assistant professor in the department of psychiatry at Virginia Commonwealth University, and colleagues examined irritability in a population-based cohort of Swedish twins via self- and parent reports. Final analysis included 1,310 twin pairs who reported on irritability four times during the study period at age 8 to 9 years, 13 to 14 years, 16 to 17 years and 19 to 20 years.

Overall, females had higher irritability scores compared with males, according to self- and parent reports.

Genetic effects differed between sexes, as males exhibited increasing heritability from early childhood through young adulthood and females exhibited decreasing heritability.

Shared environmental factors did not significantly affect irritability among males and females.

Nonshared environmental factors strongly influenced irritability in early childhood among males, and this association weakened over time. Among females, the effect between nonshared environmental factors and irritability remained relatively stable over time.

“Given the transdiagnostic nature of irritability, a better understanding of the genetic and environmental contributions to its chronic and episodic expression could inform the literature and promote development of psychological and pharmacological therapeutics,” Roberson-Nay and colleagues wrote. “Overall, genes appear to impart robust and dynamic effects on irritability throughout development, while the environment is a strong force primarily during childhood. These effects are worthy foci for future inquiry.” – by Amanda Oldt

Disclosure: Roberson-Nay reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.