'Oh, baby, please don't cry!': in infants suffering from infantile colic hypothalamic-pituitary-adrenocortical axis activity is related to poor sleep and increased crying intensity.

Background/Aim: Infantile colic (IC) is considered to represent the upper end of the spectrum of early developmental crying behavior. Little is known about hypothalamic-pituitary-adrenocortical axis activity and sleep in relation to infants’ crying. The aim of the present study was to assess cortisol secretion in infants in relation to their sleep and crying patterns. Method: Sixteen infants (mean age: 8 weeks; SD = 1.5 weeks) were enrolled. Their mothers completed a series of questionnaires regarding the infants’ crying and sleeping patterns. The infants’ sleep was objectively assessed with actigraphs. After 4 weeks, the infants were assessed once again. Cortisol secretion was measured by means of saliva samples in the mornings after awakening. Results: Morning saliva cortisol levels were related to more frequent awakening and to increased crying intensity, but not to sleep or crying duration. Over 4 weeks, both crying behavior and sleep duration decreased, but there was no association between them. Cortisol secretion did not significantly change. Conclusions: In infants suffering from IC, fragmented sleep patterns and increased saliva cortisol levels were related. Cortisol secretion seems to be related to crying intensity, but not to crying duration. Crying intensity may reflect greater physiological or psychological stress rather than mere duration of crying.