Behavioral and physiological responsivity, sleep, and patterns of daily cortisol production in infants with and without colic

To describe the behavioral and physiological responses associated with coli c, the responses of 20 two-month-old infants with and 20 without colic were studied during a physical examination. Parents kept a diary of infant beha viors (including crying and fussing) for 3 days following the visit. Using Wessel, Cobb, Jackson, Harris, & Detwiler criteria, colic was defined as fu ssing/crying for 3 hr or more on each of the 3 days. Behavioral data coded by "blind" observers showed that during the physical exam, colic infants cr ied twice as much, cried more intensely, and were more inconsolable than we re control infants. Despite these behavioral differences, heart rate, vagal tone, and cortisol measures indicated no appreciable difference in physiol ogical responsivity for the two groups. At home, parents collected saliva c ortisol samples at wakeup, midmorning, midafternoon, and evening for 2 days . In a finding similar to that shown by the laboratory data, the colic and control infants did not have different levels of daily average cortisol. Th ese laboratory and home data provide no evidence of greater responsivity in the physiological substrate of difficult temperament for colic infants and are consistent with evidence of similarity in temperament once colic is re solved. At home, compared with control infants, colic infants did display a blunted rhythm in cortisol production. By diary, they also slept about 2 h r less per day than did control infants. Nighttime sleep was still signific antly different when fussing/crying was statistically controlled. These dat a suggest that colic might be associated with a disruption or delay in the establishment of the circadian rhythm in activity of the hypothalamic-pitui tary-adrenocortical axis and associated sleep-wake activity.