Infancy predictors of functional somatic symptoms in pre- and late adolescence: a longitudinal cohort study

Physiological regulatory problems in infancy (i.e., problems with sleeping, feeding, and tactile reactivity) have been associated with impairing functional somatic symptoms (FSS) at ages 5-7. We aimed to extend this finding by examining not only the association of physiological regulatory problems but also other infancy factors (i.e., emotion dysregulation and contact problems) with FSS in pre- and late adolescence. Standardized behavioral assessments and self-report questionnaire data from assessment waves at 0-1, 11-12, and 16-17 years of the population-based Copenhagen Child Cohort (CCC2000) were linked with Danish register data on maternal postpartum psychiatric illness and family adversity as covariates. Multiple linear regression analyses were performed to examine the association between infancy factors and FSS in pre- and late adolescence. Only infancy physiological regulatory problems significantly predicted preadolescent FSS (b = 0.38, 95% CI [0.14, 0.62]), also when accounting for maternal postpartum psychiatric illness and family adversity. The association was attenuated for late adolescent FSS.

Infancy physiological regulatory problems may represent early signs of a dysregulated stress system and were found to significantly predict FSS in pre- but not late adolescence. Implications for early FSS prevention could include testing interventions promoting infants' regulation of sleep, feeding, and tactile reactivity.

• Functional somatic symptoms (FSS) are common in adolescence. • Explanatory models of FSS emphasize a multifactorial etiology involving interactions between early child-related vulnerabilities and contextual factors. • Infancy physiological regulatory problems (i.e., problems in the area of sleeping, feeding, and tactile reactivity) might represent early signs of a dysregulated stress system, and have been shown to predict impairing FSS in preschool childhood.

• This study investigated the association between infancy factors, namely physiological regulatory problems with feeding, sleeping, and/or tactile reactivity, emotion dysregulation, and contact problems, and FSS in pre- and late adolescence. • Only a combination of infancy physiological regulatory problems significantly predicted preadolescent FSS, with the association attenuating for FSS in late adolescence. • Implications for early FSS prevention could include parent-mediated interventions aiming to promote infants' physiological regulatory skills.