Excessive crying, irritability in infancy linked to smaller amygdala, behavior issues

Infants who cried excessively and were more irritable had smaller amygdala volume, as well as more internalizing and externalizing problems in childhood and adolescence, researchers reported.

“Excessive crying and irritability in infancy may reflect an early vulnerability to behavioral problems and be linked with neurobiological differences in the development of the amygdala,” Sara Sammallahti, PhD, of the department of obstetrics and gynecology at the University of Helsinki and Helsinki University Hospital in Finland, and colleagues wrote in a study published in Journal of the American Academy of Child & Adolescent Psychiatry.

To determine the association between excessive crying and irritability in infancy and behavioral problems and amygdala volume in childhood and adolescence, Sammallahti and colleagues analyzed the data of 4,751 children from the Generation R Study cohort who were born in the Netherlands from 2002 to 2006.

MRI was utilized after 10 years to measure amygdala volume, while a parent-reported survey for internalizing and externalizing behavior was conducted after 1.5, 3, 6, 10 and 14 years of follow-up.

Researchers found that infants who cried excessively had higher rates of both internalizing (effect estimate 0.2 SD units; 95% CI, 0.14-0.27) and externalizing (effect estimate 0.17 SD units; 95% CI, 0.1-0.24) behavior in childhood and adolescence. In addition, these children tended to have smaller amygdala volume at 10 years (effect estimate -0.19 SD units; 95% CI, -0.32 to -0.06).

“Observations of population-level associations between infant crying and neurobiological markers can help shed light on the likely multifaceted etiology of excessive crying,” Sammallahti and colleagues wrote.

“Furthermore, our results suggest parent-reported excessive crying should not be simply shrugged off: it could reflect one of the earliest child markers of vulnerability to develop behavioral problems.”