The causes of colic:

How disease and differences in brain chemistry can explain excessive, inconsolable crying in young babies

© 2009 - 2012 Gwen Dewar, Ph.D., all rights reserved

Why parents should consider the physiological causes of colic

Colicky infants cry excessively and inconsolably. Once a colicky baby gets going, it can be impossible to calm him down.

Why? There are many possible answers.

Long ago, people assumed that colic was caused by abdominal pain. But the link was unproven, so many researchers have adopted definitions of colic that make no reference to causation.

In fact, some have argued that colic isn’t about pain--or indeed any physical ailment. (For an overview of colic and different ideas about the causes of colic, click here.)

But there’s strong evidence suggesting that at least some colicky babies suffer from treatable diseases.

It’s also possible that most colicky babies cry because there is something different about their brain chemistry --something that makes them more easily upset and less easily soothed.

In this article, I review the scientific evidence about the physiological causes of colic. But please keep in mind:

• This information isn’t intended as medical advice, so please don’t use it as a substitute for professional medical care.

• This information isn’t intended as an endorsement of any particular kind of therapy or medication.

It’s dangerous to give babies drugs, herbal supplements, or medications of any kind without a physician’s supervision.

The purpose of this review is to help science-minded parents understand

(1) why it’s worthwhile to have your colicky baby screened for illness, even if your baby seems pretty healthy and is growing well, and

(2) why parents shouldn’t blame themselves or their babies for colic.

As I note elsewhere, there is evidence that baby care influences how much babies cry. However, there are plenty of parents who strive to do everything right, and still find themselves coping with colic.


The causes of colic: Putting the risk of disease in perspective

Some researchers have noted that less than 5% colic cases are caused by disease (e.g., Barr 1998).

However, the statistics depend on which criteria you use to define colic. When criteria include symptoms of pain or gastrointestinal distress, diseases are more likely involved.

For example, in one study, researchers included criteria like diarrhea and spasm. They found that almost 45% of these colicky babies responded favorably when treated for transient lactose intolerance (Kanabar et al 2001).

It also seems that severe infantile colic is linked with physical ailments later in life.

In one study, researchers tracked babies with severe colic. Ten years later, these kids were more likely than others to suffer from recurrent abdominal pain and/or allergies (Savino et al 2005).

Perhaps some colic cases are simply an early manifestation of long-term health problems.

So if your baby has colic, it’s important to screen her for disease. A variety of diseases can be causes of colic—diseases that include cow’s milk protein intolerance, carbohydrate malabsorption, infantile migraine, or acid reflux. I provide the details below.

Cow’s milk protein intolerance

One of the more common medical causes of colic is cow’s milk protein intolerance (Lindberg 1999). This condition can affect babies who drink formula that contains cow’s milk. It can also affect breastfed babies whose mothers consume cow’s milk products.

The cure for this problem is pretty straightforward: Eliminate cow’s milk from the diet.

In one randomized, double-blind study formula-fed babies who suffered from colic were assigned to receive cow’s milk formula. The other group of colicky babies was assigned to receive extensively hydrolyzed whey formula. At the end of one week, the babies on extensively hydrolyzed whey formula cried about an hour less each day (Lucassen et al 2000).

Experiments that substituted casein hydrolysate formula have also reported a reduction in colic symptoms (Forsyth 1989; Hill et al 1995; Lucassen et al 1998).

Carbohydrate malabsorption

Cow’s milk protein isn’t the only ingredient that babies might have trouble digesting. One intriguing, double-blind experiment gave 5-month old infants one of two types of juice—

• apple juice (which was high in sorbital and had a high fructose-to-sucrose ratio), and

• white grape juice (which had no sorbital and had a low fructose-to-sucrose ratio)

Then researchers measured how much hydrogen the babies excreted when they exhaled, an indicator of carbohydrate malabsorption. The team discovered that some babies—those who had been colicky when they were younger—showed signs of carbohydrate malabsorption after drinking the apple juice. Immediately after drinking the apple juice, these babies also cried more and slept less (Duro et al 2002).

The results imply that some colicky infants might have trouble absorbing carbohydrates.

Is transient lactose intolerance one of the causes of colic?

There is also strong evidence that some babies suffer from a transient inability to digest lactose, the sugar in milk. Transient lactose intolerance is usually caused by acute diarrhea, which damages the mucosal lining of the intestinal wall (Bartrop and Hull 1973). It can also be caused by malnutrition and cystic fibrosis.

If your baby suffers from transient lactose intolerance, your physician will probably focus on treating the cause (e.g., the diarrhea). The intestinal lining will heal and symptoms should improve within a couple of weeks. Putting your baby on a lactose-free diet is probably not worthwhile. And babies with transient lactose intolerance should continue breastfeeding (Heyman 2006; Heubi et al 2000).

But your physician might also prescribe infant-formulated drops that contain lactase, the enzyme that converts lactose into simple sugars (Buckley 2000).

Infantile migraine

This may be a relatively rare condition. It’s also difficult to identify because many of the signs of migraine are similar to signs of other illnesses…or even fatigue: intermittent head-holding, head tilting, hair- or ear-pulling, crying, irritability, vomiting, or pallor. In the case of migraines, these symptoms usually improve after a brief nap (Barlow 1994).

Might infantile migraine be one of the causes of colic—at least for a few infants? It seems very possible.

There is a case reported in the pediatric literature of a baby whose colic symptoms improved dramatically after treatment for migraine. There are also studies demonstrating a correlation between colic and childhood migraine—i.e., case control studies where researchers matched child migraine sufferers with a control group of similar, but migraine-free, children. In one study, researchers found that kids with migraine were four times as likely to have suffered from colic as babies (Jan et al 2001).

In another study of 154 mother-infant pairs, babies whose mothers had a history of migraines were 2.6 times as likely to have colic (Gelfand et al 2012).

Needless to say, parents who are worried about infantile migraine need to consult a pediatrician. And they should never give their babies any medication unless it has been specifically prescribed by a physician.

GERD (gastroesophageal reflux disease)

Sometimes the sphincter muscles at the bottom of the esophagus open up, allowing stomach contents (gas, partially digested food, or acid) back into the esophagus. That’s why babies burp and (sometimes) spit up. It’s also the cause of heartburn, or acid reflux.

When the condition is severe and chronic, it’s called GERD, or gastroesophageal reflux disease. Not surprisingly, GERD hurts and makes babies cry. Symptoms of infantile GERD include frequent vomiting, frequent hiccups, difficulty swallowing, and irritability during feeding. Babies may experience pain in the esophagus, as well as the areas around the sternum and abdomen (Bhatia and Parish 2009).

If you suspect your baby has GERD, check with your pediatrician. You might also want to read Bryan Vartabedian’s book, Colic Solved: The Essential Guide to Infant Reflux and the Care of Your Crying, Difficult-to-Soothe Baby .

Vartabedian is a pediatric gastroenterologist who underwent a kind of professional epiphany when he became a new father and his baby developed GERD. He knows how easy it can be for GERD babies to get overlooked. I wish I’d had this book when I was coping with a GERD baby.


Other causes of colic that might trigger abdominal pain

Lactose intolerance and cow’s milk protein intolerance aren’t the only conditions that can cause painful colic. Here are some others.

Evidence for cramps: Are increased gastrointestinal contractions one of the causes of colic?

Several studies suggest that colicky babies have higher levels of serum motilin, a hormone that stimulates contractions or spasms in the gastrointestinal tract (Savino et al 2007; Lothe et al 1990; Lothe et al 1987). Colicky babies may also have increased levels of ghrelin, a hormone that stimulates the appetite (Savino et al 2007).

And it’s possible that one of the causes of colic pain is related to levels of serotonin and melatonin. Serotonin increases intestinal contractions, melatonin suppresses them. In children and adults, serotonin and melatonin levels peak in the evening.

Young babies are different. Their serotonin levels peak in the evening, but their melatonin levels don’t. As a result, there isn’t enough melatonin to counteract the serotonin and babies have more cramps. This would explain why colic tends to disappear after 3 months of age. That’s when melatonin circadian rhythms mature (Weissbluth and Weissbluth 1992).

Bowel inflammation

Colicky babies might have more bowel inflammation, too. In another study of infant stools, researchers found that colicky babies had higher levels of fecal calprotectin, a marker for inflammation of the bowel (Rhoads et al 2009).

H. pylori

In a recent study comparing colicky infants with their healthy counterparts, 82% of the 55 infants with colic tested positive for the Helicobacter pylori bacterium -- the pathogen known to cause gastric pain and peptic ulcers in older people. Just 23% of control infants were infected with H. pylori (Ali 2012).

Do colicky babies have an unfavorable balance of gut microflora?

In addition to any other problems, colicky babies may have more gas-producing bacteria in their digestive tracts. In one study, researchers examined the stools of colicky babies and compared these to the stools of normal infants. The stool of the colicky babies had higher concentrations of E. coli (Savino et al 2009).

Differences in gut flora hint that colicky babies might benefit from probiotics—“friendly” microorganisms that colonize the digestive tract and help reduce bowel inflammation. And indeed, this seems to be true.

Probiotics for colicky babies

In a randomized study of colicky, breastfed infants, Savino and colleagues assigned some babies to receive supplements of the probiotic Lactobacillus reuteri (American Type Culture Collection Strain 55730), and other babies to receive supplements of simethicone.

After 28 days, the 95% of probiotic babies were crying less (the median crying time having dropped from 159 minutes/day to 51 minutes/day). By contrast, only 7% of the simethecone babies showed any reduction in crying time (Savino et al 2006).

You might wonder if researchers “stacked the deck” by selecting babies who had previously shown signs of digestive illness. They did not. When recruiting their subjects, Savino’s team excluded any babies that had clinical evidence of chronic illness or gastrointestinal disorders.

A more recent, double-blind randomized study of 80 colicky infants has also reported reduced symptoms in infants given L. reuteri (Szajewska et al 2012).

Are probiotics worth trying? Maybe. But check with your pediatrician first. In some patients—such as those with impaired immune systems—probiotics could be dangerous. Moreover, the quality of over-the-counter probiotics vary greatly, and different species or strains of probiotics work differently. For more information, see this evidence-based article about probiotics for children.


And what about the brain? Do colicky babies have different brain chemistry?

Whether or not your baby suffers from a disease that makes him cry, it's also possible that he's just different. Research suggests that colicky babies might respond differently to stimulation (St James-Roberts et al 2003).

The same things that don't bother normal babies much--like being undressed or handled--can really upset colicky infants.

And it appears that colicky infants might respond differently to potentially soothing stimuli--like sweet flavors.

For more information, see this story about colic and the brain.



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References: The physiological causes of colic

For full citations of the studies cited in this article, click here.

Content of "Causes of colic" last modified 12/12

image of crying infant by David Buchwald / wikimedia commons

image of H. pylori bacteria by Patho / wikimedia commons