SPOILER ALERT! ~ Biological markers can help understand why some infants are more vulnerable to their mother's stress and anxiety than others. ~ Respiratory Sinus Arrhythmia (RSA) is one relevant biological marker that helps explain this difference. ~ RSA refers to the normal heart rate beats during inspiration compared to expiration. ~ High RSA is usually a good sign, because it indicates the ability to regulate one’s emotions as opposed to getting stuck in one emotion. ~ High RSA is usually a good sign, because it indicates the ability to regulate one’s emotions as opposed to getting stuck in one emotion. However, RSA increases susceptibility to the effects of environmental factors since it means more emotional reactivity ~ High RSA in infants with anxious mothers exhibit more emotional and problem behaviors than those with low RSA who are in a similar situation.
There is growing evidence that maternal prenatal stress and anxiety are associated with infant’s increased negative affectivity (e.g., frequent crying, emotional distress to limitations and unfamiliarity) and problem behaviors in later childhood. However, other studies demonstrate that not all infants are susceptible to such influences, and for example, elevated maternal prenatal anxiety does not predict negative affectivity in infants with a specific genetic variation at the level of the neurotransmitter Serotonin.
Respiratory Sinus Arrhythmia (RSA)
Investigations into biological markers that could potentially moderate the infant’s susceptibility to maternal prenatal stress reveal that infant’s respiratory sinus arrhythmia (RSA) could be one such marker. RSA refers to the normal fluctuations in heart beats during inspirations compared to expirations. It typically indicates parasympathetic dominance (i.e., which indicates a relaxed and calm state) over sympathetic arousal .
For example, previous studies have associated higher baseline RSA (i.e., high RSA at rest) with better emotion regulation and executive functioning. However, other studies have also reported that infants with higher RSA exhibit more emotional reactivity under both positive and negative situations, which suggests that the effects of RSA on the individual are contingent upon their environment and may result in either negative or positive outcomes.
For example, high-baseline-RSA infants reared in poverty but with secure attachment (i.e., involved and caring parents) express the least amount of problem behaviors compared to those with insecure attachment (i.e., indifferent and distant parents). Furthermore, quality of attachment is not related to the amount of problem behaviors among low-baseline-RSA infants.
These results support the hypothesis that RSA can lead to positive or negative outcomes depending on environmental factors, and in this case high RSA coupled with secure attachment leads to positive outcomes. Conversely, children with low RSA do not exhibit problem behaviors as a result of the quality of attachment (i.e., secure or insecure).
Infants with low RSA are unaffected by their mother’s Anxiety
In addition, results from the current study support the role of RSA as moderating the influence of maternal prenatal anxiety (i.e., acts as an environmental factor) over the infant’s developing temperament. Particularly, the authors found that infants 8-10 months of age with high baseline RSA exhibit higher levels of negative affectivity following the mother’s increased stress during the prenatal period. Conversely, infants with low baseline RSA appear unaffected (i.e., absence of high negative affect) by their mother’s anxiety level during their pregnancy.
Thus, In line with previous findings RSA becomes an indicator of the child’s emotional and behavioral outcomes when exposed to their mother’s anxiety. More specifically RSA frequency (high versus low) under exposure to maternal stress and anxiety is what determines how the child will develop emotionally and behaviorally.
The authors conclude that RSA moderates the association between maternal prenatal anxiety and infant’s propensity towards negative affectivity by way of higher overall reactivity. Notably, infants with high RSA exhibit higher reactivity to external cues, which in turn allows them to be more responsive to their environment and facilitate adaptation to it.
Peltola, MJ, Mäkelä, T, Paavonen, EJ, Vierikko, E, Saarenpää‐Heikkilä, O, Paunio, T, Hietanen, JK, Kylliäinen, A. Respiratory sinus arrhythmia moderates the impact of maternal prenatal anxiety on infant negative affectivity. Dev Psychobiol 2017; 59: 209– 216. https://doi.org/10.1002/dev.21483