Colicky babies and the brain: Understanding the effects of temperament, stress reactivity, and pain sensitivity

colicky baby crying in father's arms

By definition, colicky babies cry excessively and inconsolably. But why? Sometimes it’s because babies are suffering from a physical ailment — like allergies, migraine, or gastroesophageal reflux disease. In these cases, symptoms of colic may include:

  • gastric distress (such as diarrhea and vomitting);
  • signs of muscle tension (such as an arched back, clenched fists, and a swollen, hard abdomen); and
  • other indicators of pain (such as a cry that sounds different than usual — more intense or high-pitched).

If you observe any of these symptoms, you should talk with your medical provider.

But let’s say you aren’t noticing evidence of gastric distress, muscle tension, or pain. Your baby is nevertheless crying a lot — so much so that your baby meets the “rule of three” criteria: crying for more than 3 hours a day, at least 3 times per week. What else might explain all of this unstoppable wailing?

Unfortunately, some people jump to the conclusion that the parents are to blame. (“The parents of colicky babies must be doing things differently. They must be less sensitive or less responsive than other parents…”)

In reality? Parenting (and other environmental factors, including cultural ones) can influence how and when an infant cries. But another important part of the picture concerns individual differences between babies. We could put two different babies in the same kind of environment — and provide them with the same kind of care — and end up with very different outcomes.

This is clear from people’s everyday experiences. Just ask parents who have raised multiple children! But there’s scientific evidence, too. Research suggests that some infants are “wired up” a little differently. These babies may tend to

  • show higher levels of emotional negativity;
  • experience greater reactivity to sensory stimulation;
  • respond atypically to caregiving maneuvers that other infants finding soothing;
  • lack the daily, hormonal rhythms that help infants wind down at night; or
  • feel a heightened sensitivity to pain.

And if you’re struggling with these problems, it’s reassuring — and empowering — to understand them. Instead of feeling blameworthy or helpless, you can acknowledge that your baby is quirky, and work on practical ways to help you and your baby cope. So let’s take a closer look at what the research tells us.

What’s special about colicky babies?

“Temperament” refers to the individualistic ways that a child responds to the environment. This includes emotional and physiological reactions (does the child tend to be inhibited? energetic? easily upset?), as well as patterns of sociality, attentiveness, and self-regulation (Aktar and Perez-Edgar 2020; Shiner et al 2012). Researchers have documented differences in temperament very early in life — within days of birth (Tsuchiya 2011). In fact, it appears these differences can be tracked before birth, and there is evidence that genetic factors play a role.

For example, in one study, Blair Pingeton and her colleagues used ultrasound to measure the heartbeats of 34-week-old fetuses. What did they find? The fetuses with faster heart rates were more likely – after birth – to display higher levels of negative emotion (Pingeton et al 2021).

Other research indicates that certain genetic variants in newborns – like the 5-HTTLPR S and MAOA L alleles – are linked with greater stress reactivity and / or a slower recovery of cortisol levels following a brief stressor (like a medical jab to the heel to collect blood). These babies are also more likely to show negative emotionality and poorer self-regulation by the age of 3 months (Bajgarova and Bajgar 2020).

There is also evidence that the brains of colicky infants are more emotionally reactive to certain types of sensory stimulation

For instance, consider the study where researchers subjected 91 young infants to a series of everday handling maneuvers — including being undressed, getting a diaper change, and being laid down. The infants who became the most upset or reactive during these tests were about twice as likely to show symptoms of colic at home (St James-Roberts et al 2003).

And, more recently, researchers at the University of Geneva have shown links between colic symptoms and the way a baby’s brain processes sensory information.

It began in a laboratory with functional magnetic resonance imaging (fMRI). Using this technology, Alexandra Adam-Darque and her colleagues monitored the brain activity of 21 newborns while the babies were presented with a pungent smell: The odor of rotten cabbage.

Next, the babies went home and resumed their normal daily lives. When the babies were 5-6 weeks old, their parents kept a “crying diary” — recording all episodes of crying and fussing over a period of 2 weeks. Based on these records, some of the babies met the criteria for colic, and there were strong links with the previous fMRI results (Adam-Darque et al. 2021).

The babies who had developed colic were the same infants who had — weeks earlier — shown heightened brain activity in response to the odor. Moreover, this heightened activity hadn’t just taken place in brain regions associated with olfactory processing. The colicky babies had also experienced greater activation in areas associated with the processing of negative emotions and pain (for the brain nerds among you: the amygdala, the middle cingulate gyrus, thalamus, caudate nucleus, and putamen).

So maybe colicky babies are simply less tolerant of stresses, disruptions, transitions, and other potentially noxious stimuli.

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). And it appears that colicky infants react differently to caregiving maneuvers that are meant to soothe.

For instance, in a couple of experiments, researchers assigned Western parents to care for the babies the way that traditional hunter-gatherers do: Hold or carry the baby at least 80% of the time. If your baby cries, respond within seconds by feeding or soothing the infant.

What happened when parents used this approach? It reduced crying in normal babies, but not in babies with who had been diagnosed with colic (Hunziger and Barr 1986; Barr et al 1991). The same attempts to soothe didn’t have the same effect.

Similarly, when Ronald Barr and his colleagues gave 6-week old babies a sugar solution to taste, the researchers 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 1999).

Why this difference? Perhaps, Barr speculates, something is wrong with the system that rewards the brain with endogenous opioids — natural, self-produced painkillers. In normal babies, the sugar is a signal for the brain to release these feel-good drugs. In colicky babies, this response is impaired (Barr 1999). According to this hypothesis, colic eventually improves because the opioid release system matures.

Another possibility concerns circadian rhythms — the cyclic, daily production of hormones, like melatonin and cortisol

If babies don’t produce enough melatonin at night, it could interfere with their ability to wind down and sleep well. This, in turn, could worsen their moods, and make them more intolerant of pain and discomfort (Leuchter et al 2013; Cohen et al 2012). It’s also possible that patterns of cortisol production could impact infant sleep (White et al 2000; Kiel et al 2015).

Do colicky infants show any differences in their circadian rhythms? Maybe. In a study tracking 55 children, babies with colic were slower to develop mature rhythms of melatonin production. They also showed less defined daily rhythms of cortisol (İnce et al 2018), which is consistent with other research (White et al 2000).

Finally, there is the theory that colicky babies have more pain receptors in their intestines…making them more sensitive to pain. 

We’ve seen how colicky infants might experience enhanced responsiveness in brain areas that process pain. I’ve also mentioned (in the introduction) that colic symptoms can be linked to painful gastric conditions.

In particular, researchers have amassed compelling evidence that babies with colic have a different mix of bacteria in their large intestines. Compared with non-colicky infants, they are more likely to have high concentrations of the type of bacteria that can cause inflammation and excess gas. They may also have lower concentrations of the “good,” probiotic bacteria.

This alone might explain the crankiness of colicky infants: They might have low grade inflammation of the gut. But there’s more. Researchers speculate that the imbalance of gut flora might also activate nerve receptors in the intestines, making babies more sensitive to abdominal pain (Pärtty and Kalliomäki 2017; O’Mahoney et al 2016).

If this is the cause of an infant’s problems, it’s possible that physician-supervised doses of the probiotic bacteria, Lactobacillus reuteri, could help. But the research on this subject is mixed (Pärtty and Kalliomäki 2017). In some studies of breastfed babies, probiotic treatment helped substantially. In other studies, it made little difference.

More studies are needed to understand why probiotics don’t always work. One likely factor is that it depends on an individual’s pre-existing mix of bacteria (Pärtty and Kalliomäki 2017). This may vary according to local differences in diet, and other environmental factors. Simply adding probiotics might not crowd out enough of the troublesome bacteria — not for some babies. In addition, it’s important to understand that probiotics therapy isn’t safe for babies with impaired immune systems.

So you shouldn’t attempt probiotics therapy without guidance from your doctor. But it’s worth looking into, so ask your doctor if he or she thinks is appropriate approach for your baby.

More to learn

What else do parents need to know about colic? Pediatricians urge parents to remember that in most cases, colic symptoms usually improve by 4 to 6 months. But meanwhile, coping with a colicky infant can be very stressful — so stressful that it can cause depression and anxiety. It also raises the risk that a parent will impulsively shake an infant, which can cause tragic injuries. So if your baby is crying excessively or inconsolably, you are right to take the problem seriously. If your baby is crying to a degree that concerns you, definitely discuss this with your medical provider.

For an evidence-based guide to the ways that doctors diagnose colic, see my article “What is colic?” It includes a discuss of tactics that might help soothe colicky babies — white noise, rocking, and walking. For additional information about the helpfulness of rocking and walking, see my article, “How to soothe a crying baby to sleep.”

Want to know more about ailments that can cause colic symptoms? See my article, “The physiological causes of colic: How ailments and neurological differences can sometimes explain excessive, inconsolable crying.”

And for an evidence-based discussion of the infant stress response and how to cope with it, see my Parenting Science article, “Stress in babies: How to keep infants calm, happy, and emotionally healthy.”

References: Colicky babies and the brain

Adam-Darque A, Freitas L, Grouiller F, Sauser J, Lazeyras F, Van De Ville D, Pollien P, Garcia-Rodenas CL, Bergonzelli G, Hüppi PS, Ha-Vinh Leuchter R. 2021. Shedding light on excessive crying in babies. Pediatr Res. 89(5):1239-1244.

Aktar E and Perez-Edgar K. 2020. “Infant emotion development and temperament.” In J. J. Lockman and C. S. Tamis-LeMonda (Eds.), The Cambridge Handbook of Infant Development (pp. 715- 741). Cambridge University Press.

Bajgarova Z and Bajgar A. 2020. The relationships among MAOA, COMT Val158Met, and 5-HTTLPR polymorphisms, newborn stress reactivity, and infant temperament. Brain Behav. 10(2):e01511.

Barr RG, McMullan SJ, Spiess H, Leduc DG, Yaremko J, Barfield R, Francoeur TE, Hunziker UA. 1991. Carrying as colic “therapy”: a randomized controlled trial. Pediatrics. 87(5):623-30.

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.

Cohen EA, Hadash A, Shehadeh N, Pillar G. 2012. Breastfeeding may improve nocturnal sleep and reduce infantile colic: potential role of breast milk melatonin. Eur J Pediatr  171:729–32

Hunziker UA and Barr RG. 1986. Increased carrying reduces infant crying: a randomized controlled trial. Pediatrics. 77(5):641-8.

İnce T, Akman H, Çimrin D, Aydın A. 2018. The role of melatonin and cortisol circadian rhythms in the pathogenesis of infantile colic. World J Pediatr. 14(4):392-398.

Kiel EJ, Hummel AC, Luebbe AM. 2015. Cortisol secretion and change in sleep problems in early childhood: Moderation by maternal overcontrol. Biol Psychol. 107:52-60.

Leuchter HVR, Darque A, and Hüppi PS. 2013. Brain maturation, early sensory processing, and infant colic Journal of Pediatric Gastroenterology and Nutrition.57: S18-S25

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.

O’Mahony SM, Dinan TG, Cryan JF. 2016. The gut microbiota as a key regulator of visceral pain. Pain 58(1):S19–S28.

Pärtty A and Kalliomäki M. 2017. Infant colic is still a mysterious disorder of the microbiota-gut-brain axis. Acta Paediatr. 106(4):528-529.

Pingeton BC, Goodman SH, Monk C. 2021. Prenatal origins of temperament: Fetal cardiac development & infant surgency, negative affectivity, and regulation/orienting. Infant Behav Dev. 65:101643.

Shiner RL, Buss KA, McClowry SG, Putnam SP, Saudino KJ, Zentner M. 2012. What is temperament now? Assessing progress in temperament research on the Twenty‐Fifth Anniversary of Goldsmith et al.(). Child Development Perspectives. 6(4):436-44.

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.

White BP, Gunnar MR, Larson MC, Donzella B, Barr RG. 2000. Behavioral and physiological responsivity, sleep, and patterns of daily cortisol production in infants with and without colic. Child Dev. 71(4):862-77.

image of colicky baby in father’s arms by Atstock productions / istock

content last modified 2/2023

For references cited in my other articles about colic, click here.

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