Individual differences of temperament have been observed during
the first few days postpartum (Tsuchiya 2011), and to some degree, you
can predict which newborns will become colicky by seeing how they
respond to being undressed, handled, or put down. The babies who are
most upset by these maneuvers are most likely to develop colic (St
James-Roberts et al 2003).
So maybe colicky babies are simply less tolerant of disruptions and transitions.
Consistent with this idea, several studies have found that colic
symptoms improve when parents are instructed to stimulate their babies less (Lucassen et al 1998).
There’s another possibility, too: Colicky babies may also
react differently to care-giving maneuvers that are meant to soothe
In normally-developing infants, some calming stimuli can trigger
the release of endogenous opioids, self-produced painkillers that bathe
the brain. Soothing touch can also trigger the brain to release
oxytocin, a hormone and neurotransmitter that counteracts stress. Do babies with colic respond the same way?
As noted above, research suggests that the real difference
between babies with and without colic is that colicky babies have more
trouble calming down once they begin crying. In one controlled study,
researchers found that normal and colicky babies had the same frequency
of crying bouts. However, the babies with colic cried longer (Barr et al 1992).
This is consistent with the “Pleistocene" baby care experiments that I mention in my review of the research about colicky babies.
Increased carrying and breastfeeding reduced crying in normal babies, but not in babies with colic (e.g., Barr et al 1991).
And an experiment with soothing flavors reported similar results.
Ronald Barr and colleagues gave 6-week old babies a sugar solution to
taste, and discovered that all babies—those with colic and those
without—responded to the sugar by calming down.
But the calming effect lasted longer for normal infants. Babies with colic were more likely to resume crying two minutes later (Barr et al
Why these differences? Barr’s team speculates these babies
may have a less responsive distress regulation system: Perhaps soothing
stimuli are less effective triggers of endogenous opioids (Barr 1999).
According to this idea, colic eventually improves because the opioid
release system matures.
As of 2013, I haven’t found any studies that address the oxytocin
and colic. It would be interesting to know if colicky babies release
less oxytocin in response to soothing stimuli.
Meanwhile, it seems a good guess that some babies cry excessively
and inconsolably because of differences in chemically-mediated
Barr RG, Young SN, Wright JH, Gravel R, and Alkawaf R. 1999.
Differential calming responses to sucrose taste in crying infants with
and without colic. Pediatrics. 103(5):e68.
Barr RG, Rotman A, Yaremko J, Leduc D and Francoear TE. 1992. The
crying of infants with colic: A controlled empirical description.
Pediatrics 90: 14-21.Barr 1999
Lucassen PL, Assendelft WJ, Gubbels JW, van Eijk JT, van Geldrop
WJ, Neven AK. 1998. Effectiveness of treatments for infantile colic:
systematic review. BMJ. 316(7144):1563-9.
St James-Roberts I, Goodwin J, Peter B, Adams D, and Hunt S.
2003. Individual differences in responsivity to a neurobehavioural
examination predict crying patterns of 1-week-old infants at home
Developmental Medicine & Child Neurology 45(6):400-407.
Tsuchiya H. 2011. Emergence of temperament in the neonate:
neonates who cry longer during their first bath still cry longer at
their next bathings. Infant Behav Dev. 34(4):627-31.
content last modified 5/2013
For references cited in my other articles about colic,