What is colic? A guide for the science-minded parent

© 2009 - 2018 Gwen Dewar, Ph.D., all rights reserved

Colicky babies cry excessively and inconsolably. But what is colic, really?

Today, many doctors define "infantile colic" according to the "rule of three," which identifies babies as colicky if they cry or fuss at least 3 hours each day, for 3 or more days each week. 

Babies should follow this pattern for at least 3 weeks straight, and appear "otherwise healthy," i.e., crying shouldn't be the consequence of an obvious ailment (Wessel et al 1954). If your baby is crying because she has diaper rash, nobody calls it colic.

Defined this way, the word "colic" doesn't refer to a disease, illness, or injury. If we say an infant has colic, it's a bit like saying a patient has a poor appetite. It's a description of a symptom, not a diagnosis or explanation. 

But it's clearly a symptom that matters. Even if non-stop irritability meant nothing whatsoever about the state of a baby's well-being -- even if all colicky babies were perfectly healthy and happy -- colic would still rate as a potentially serious problem. Why?

Why colic is no joke

1. Caring for a colicky baby can be very stressful, so much so that parents sometimes make terrible, tragic mistakes.

Studies suggest that inconsolable crying is a trigger for baby shaking, an act that can cause head trauma and brain damage (Barr et al 2006; Lopes and Williams 2016).

2. Colic can threaten a parent's mental health, and harm family relationships.

Studies indicate that mothers are more likely to become depressed when their babies cry inconsolably (Maxted et al 2005; Vik et al 2009; Radesky et al 2013; Petzoldt et al 2017). Fathers, too, may be at higher risk for depression (Cook et al 2017).

Colic linked with poorer interactions between infants and parents (Räihä et al 2002). And when parents are depressed, babies are at higher risk for developing insecure attachment relationships (Murray and Cooper 1997; Akman et al 2006), perhaps because parents are struggling with feelings of helplessness, anger, or rejection (Pauli-Pott et al 2000).

So if you're a parent struggling with a colicky baby, you deserve to be taken seriously. And you should know you aren't alone.

Colic is found in both breastfed and formula-fed infants. It's found among babies born pre-term and babies born full-term. Exposure to tobacco smoke is a risk factor, but colic is also common among the infants of nonsmokers.

Colic has been documented colic over the world, from China to the United States; India to Brazil; the Netherlands to Nigeria (Chen and Chwo 2006; Barr 1998; Ismail and Nallasamy 2017;  Santos et al 2015; Smarius et al 2017; Oshikoya et al 2009).

So what's really going on? What is colic from the standpoint of an infant's physiology, health, and well being? There is no single, straightforward answer to this question.

In part, this is because experts have gone out of their way to define colic as crying that has no obvious cause.

What is colic?

How the medical profession has changed its criteria over time

In earlier times, people agreed on a different definition for "colic" -- one that included symptoms of abdominal pain. People spoke of "colic" in the same way that we speak of headaches. They might have lacked a scientific understanding of what was causing colic, but the word itself had been coined to describe pain in the area of the large intestine (the colon).

Thus, identifying a baby as "colicky" meant you believed the baby was in pain, most likely because of an ailment of the gastro-intestinal tract. Was colic caused by gas?  Constipation? An obstruction? Gastro-esophageal reflux? A food intolerance? The precise causation was in doubt. But if you wanted to try to solve the problem, you knew where to look.

Nowadays, "infantile colic" seems more mysterious, but that's mostly because we've changed the definition to something even more nebulous and vague: unexplained, excessive crying.

In addition to gastro-intestinal problems, colic might be caused by troubles elsewhere in the body, brain, or environment. Does the baby suffer from migraines? Ear aches? A urinary tract infection? Does the baby have a "high strung"  temperament that makes him or her overreact to stimulation? Does the baby cry because he or she needs more "hands-on" care? Is the baby's brain simply too immature to regulate its emotional responses?

No wonder, then, there is no simple answer to the question of what causes colic. Babies may cry excessively for a variety of reasons. They might experience pain from a variety of conditions. The cause of colic can vary from infant to the next.

But this answer is incomplete. Granted, no single cause can explain every case of excessive crying. But when people ask "what is colic?" they are usually wondering if there is a single, important, underlying cause that can explain many of the cases.

Might a sizeable portion of all colicky babies be crying for the same reason? Do they have something in common that is making them cry so excessively and inconsolably?

21st century discoveries shed light on the physiological basis of colic

There is good evidence linking colic with underlying physical conditions, especially if we adopt a definition of colic that includes specific symptoms of pain or illness. 

For example, when researchers identified colicky babies using criteria that included diarrhea and intestinal cramps, they found that many of these babies suffered from transient lactose intolerance. Thirty-eight percent of infants defined as "colicky" experienced improvements after being treated for this problem (Kanabar et al 2001).

Similarly, if we examine the subset of colicky babies that have abnormal stools and a family history of allergies, we're more likely to find that food allergies are causing the trouble (Nocerino et al 2015)

And recent research consistently points to the importance of gut flora.

Babies who develop colic are more likely than others to harbor the wrong bacteria in their intestinal tracts. They have higher than normal concentrations of bacteria that could cause gas and inflammation (DuBois and Gregory 2016; Pham et al 2017; Pärtty and Kalliomäki 2017; Savino et al 2017). Many also have lower than normal concentrations of the "good" bacteria, probiotics like Lactobacillus and Bifidobacteria (deWeerth et al 2013). 

How might gut flora be related to fussing and crying?

Researchers are still trying to piece together the puzzle. But for now, they speculate that an imbalance of bacteria types may make colicky babies more susceptible to intestinal pain. They may grow more pain receptors in the gut, making the babies more sensitive to potentially painful stimuli, like the movement of gas (Pärtty and Kalliomäki 2017).

So how should we determine if a baby has colic, and what should we do about it? Let's tackle these questions in greater detail.

Understanding the developmental crying curve: What is normal, and what is colic?

All healthy, young babies cry and fuss--sometimes inconsolably, and frequently without any obvious cause. Typically, crying is more common in the late afternoon and evening.

It also seems that most healthy babies cry according to a developmental schedule.

For example, when Dieter Wolke reviewed studies conducted in Europe, North America, Australia, and Japan, he found that babies everywhere tended to cry a lot during the first 6 weeks postpartum. At 5-6 weeks postpartum, the average (mean) amount of crying was about 130 minutes a day. But 25% of babies were crying for three hours a day or more.

By contrast, at 10-12 weeks, mean crying time had dropped to below 70 minutes per day. Only 0.6% of infants this age were crying more than 3 hours a per day (Wolke et al 2017).

This, then, is the normal pattern for infants in Western countries and Japan: Lots of crying at first, with a decline after 6 weeks. Research suggests it's also the norm elsewhere, including some hunter-gatherer societies (Barr et al 1991).

So what is colic? Where should we draw the line between normal and abnormal?

As noted above, many physicians and researchers use the "rule of three," borrowed from a scheme introduced by Morris Wessel.

According to Wessel, a baby could be identified as colicky if he or she was  "otherwise healthy and well-fed" but had "paroxysms [fits] of irritability, fussiness, or crying lasting for a total of more than 3 hours a day and occurring on more than 3 days in any week" (Wessel 1954).

With some tweaks, this has become the accepted standard for defining infantile colic. It's different from the older, traditional definition -- still found in non-medical dictionaries -- that characterizes colic as severe abdominal pain. The "rule of three" eliminates references to abdominal pain, or indeed any sort of pain at all. Instead, it focuses on how much time babies spend crying.

In so doing, the "rule of three" lumps together a very broad range of potential problems, making it difficult to interpret the results of scientific studies. When researchers test a new colic therapy on a group of babies, they can't always know why it didn't work. Is the therapy truly ineffective? Or is the therapy effective, but only for a subset of colicky babies who suffer from the same underlying medical condition?

If we answer the question "what is colic" in vague terms, we're almost certainly going to miss important clues.

Of course, it can be hard to know what a baby's symptoms are. They can't talk and tell us. And it's important for physicians to start their examinations with an open mind about the cause of excessive crying, and avoid jumping to the conclusion that every case reflects gastric distress.

But I think we can do better than the "rule of three." It's an arbitrary rule for deciding if a baby cries "too much," one that depends exclusively on time. In the real world, judgments about crying "too much" aren't purely a function of time spent crying, but also on the kind of care that a baby receives.

What if a baby cries a lot because she is hungry, or because he needs reassurance and comfort? If a baby cries more than three hours a day because care-givers are slow to respond, we are less likely to regard the crying as excessive. The baby is signaling for something, and, when it doesn't come, the baby becomes more distressed.

We can call such babies colicky if we like. But doing so lumps together two very different types of babies -- (1) those who stop crying once they receive responsive care, and (2) those who don't.

Many parents are desperate for help precisely because their best attempts at soothing fail. Increased carrying or feeding isn't the solution, because parents are already trying this. If a remedy exists, it's going to be something else.

For this reason, I think an important criterion for colic is that the colicky baby is hard to soothe.

Research supports this idea. Colicky babies don't cry more frequently than other babies do. But once they get started, they take longer to quiet down, and are more likely to be inconsolable (Barr et al 1992; Barr 1998; Barr et al 2005).

In addition, research suggests that colicky babies are upset by things that don't bother normal babies very much. Some newborns are much distressed by being undressed, handled, or put down, and these babies are more likely to develop colic (St James-Roberts et al 2003).

What about other symptoms?

Some researchers don't rely on "rule of three." They adopt a more narrow conception of colic that's in line with the historical meaning of the term. These researchers recognize additional signs (Soltis 2004), including

  • evidence of muscle tension and signs of pain (e.g., clenched fists, flexed legs, arched back, a hard, distended abdomen, and grimaces)
  • high-pitched crying, and
  • signs of gastric distress (flatulence, regurgitation, vomiting, diarrhea)

Babies meeting these additional criteria are more likely to suffer from digestive problems or organic disease. Some symptoms -- like a hard, distended abdomen and flexed legs -- might indicate an intestinal obstruction. It's rare, but very dangerous, so if you observe these symptoms you should consult your doctor right away.

So whether or not we decide to define colic using the vague "rule of three," it's important to look for additional signs of pain and illness.

How can we help families struggling with colic?

The first step is to acknowledge the baby's symptoms, and recognize the possibility that they reflect a real ailment or disease. That might seem obvious, but it doesn't always happen.

That doesn't happen, in part, I suspect, because of a lag between cutting edge research and medical practice. In the 1950s, researchers failed to find evidence that "colicky" criers were especially troubled by gastric problems. They were no more likely than babies in control groups to have excess gas in the intestines, chronic diarrhea, or constipation (Illingworth 1954; Taylor 1957). At the turn of the millennium, researchers concluded that less than 5% colic cases were attributable to disease (e.g., Barr 1998).

Today the picture has changed. It's become clear that colic is linked with a distinctive physical profile, and doctors need to get caught up with the research.

As noted above, twenty-first century studies have consistently found that "colicky" babies have a different mix of bacteria colonizing their intestines. This might render babies more sensitive to intestinal pain, and it may help explain other links between colic and gastro-intestinal problems.

  • Colicky babies are more likely than other infants to suffer from transient lactose intolerance, cow's milk protein intolerance, carbohydrate malabsorbtion (Iacono  et al 1991; Barr 1998; Duro et al 2002).
  • They are at higher risk for developing bowel inflammation (Olafsdottir et al 2002; Rhoads et al 2009), and they are more likely to test positive for Helicobacter pylori, the bacterium known to cause gastric pain and peptic ulcers (Ali 2012).
  • Colic could also be a sign that your baby suffers from GERD, or gastroesophageal reflux disorder (Vandenplas et al 2004).

In addition, there is evidence that at least some colicky babies are suffering from infantile migraine (Vandenplas et al 2004; Romanello et al 2013; Gelfand et al 2015; Qubty and Gelfand  2016; Sillanpää and Saarinen 2015).

So contrary to earlier claims, it seems there are detectable, physiological difference between colicky and non-colicky babies. This doesn't mean that most colicky babies suffer from serious medical problems, or that colic won't go eventually go away. As mentioned above, most babies have improved by 12 weeks.

But these discoveries clear up some of the mystery, and help us find constructive solutions. For more information about the physiological causes of colic, see this article.  

What is colic?
Other explanations

Are these gastro-intestinal conditions the only possible causes of colic?

No. As noted above, there is evidence that some babies are more temperamental, more easily distressed by everyday experiences. Their brains might respond differently to both disruptive and soothing stimuli. For more information, see this article about colic, temperament, and the brain. 

In addition, some researchers have suggested that colic is caused by insufficient "hands-on" care. According to one theory, colic is caused by child-rearing practices that minimize responsiveness and physical contact between parents and babies. Thus, colic might be prevented if caregivers adopted a highly responsive, tactile approach to baby care--

  • holding or carrying the baby at least 80% of the time, and
  • giving the baby a breast or otherwise soothing him within seconds of hearing him cry.

But while this approach may reduce crying in normal, non-colicky babies (Hunziger and Barr 1986), experimental research has failed to show that it reduces crying time in babies diagnosed with colic (Barr et al 1991b). Perhaps that's because the parents who volunteered for this study were the sort who had already tried -- and failed -- to remedy colic by increasing responsive care. Their babies belonged to the subset of colic sufferers who are inconsolable.

Another care-giving theory of colic concerns stress. According to this idea, babies become colicky because their parents are anxious, depressed, or otherwise distressed. This isn't implausible, because babies can sense and mirror the stress of their care-givers. Moreover, there is evidence suggesting that women are less likely to report colic in their infants if they have supportive partners (Alexander et al 2017).

But it's also evident that colic causes stress in parents. Which comes first, the parental stress or the colic? Like the "hands-on" theory, the parental stress theory lacks strong evidence in its favor.

The bottom line? 

While I don't doubt that care-giving has crucial effects on babies, it's wrong to assume that babies have colic because their parents aren't being responsive, affectionate, or patient enough.

What is colic? 
More reading

For more information relevant to baby colic, see these articles:






References: What is colic?

For the studies cited in this article, see "What is colic? A bibliography of scientific studies about the causes of colic"


Content last modified 2/2018


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