Objective Early life stress has been shown to influence the developing autonomic nervous system. Stressors in infancy may program the autonomic nervous system resting state set point, affecting cardiovascular function in later life. Excessive crying may be an indicator of increased stress arousal in infancy. We hypothesized that excessive infant crying is related to altered cardiac autonomic nervous system activity and increased blood pressure at age 5–6 years. Methods In the Amsterdam Born Children and their Development study, excessive crying, maternal burden of infant care and maternal aggressive behavior in the 13th week after birth (range 11–16 weeks) were reported using questionnaires. Blood pressure, heart rate, heart rate variability and indicators of cardiac autonomic nervous system activity (sympathetic drive by pre-ejection period, parasympathetic drive by respiratory sinus arrhythmia) were measured at age 5–6 years during rest. Inclusion criteria were singleton birth, term-born, and no reported congenital or cardiovascular problems (N = 2153 included). Results Excessive crying (2.8%) was not associated with resting heart rate, heart rate variability, pre-ejection period, respiratory sinus arrhythmia nor with blood pressure at age 5–6 years. Conclusions Excessive infant crying as an indicator of increased stress arousal does not seem to be related to resting activity of the autonomic nervous system or blood pressure at age 5–6. Potential associations may become visible under stressed conditions.

Early life stress has been shown to contribute to alterations in biobehavioral regulation. Genetic make-up, especially related to social sensitivity, might affect the child’s vulnerability to these alterations. This study examined whether maternal verbally aggressive behavior in early infancy interacts with oxytocin polymorphisms in changing resting cardiovascular outcomes at age 5–6. In the Amsterdam-Born-Children-and-their-Development-(ABCD)-study, a large prospective, observational, population-based birth cohort, maternal verbally aggressive behavior was assessed in the 13th postnatal week (range 11–25 weeks, SD 2 weeks) by a questionnaire (maternal self-report). Indicators of resting cardiac autonomic nervous system activity (sympathetic drive by pre-ejection period, parasympathetic drive by respiratory sinus arrhythmia), heart rate, and blood pressure were measured at age 5–6 years. Data on oxytocin receptor gene polymorphisms rs53576, rs2268498 and oxytocin polymorphisms rs2740210, rs4813627, were collected (N = 966 included). If the child was carrier of the rs53576 GG variant, exposure to maternal verbally aggressive behavior (10.6%) was associated with increased systolic blood pressure at age 5–6 (B = 4.9 mmHg,95% CI[2.2;7.7]). If the child was carrier of the rs2268498 TT/TC variant, exposure to maternal verbally aggressive behavior was associated with increased systolic blood pressure at age 5–6 (B = 3.0 mmHg,95%CI[1.0:5.0]). No significant interactions of maternal verbally aggressive behavior with oxytocin gene polymorphisms on heart rate or cardiac autonomic nervous system activity were found. In conclusion, oxytocin receptor gene polymorphisms may partly determine a child’s vulnerability to develop increased systolic blood pressure after being exposed to maternal verbally aggressive behavior in early infancy.