Infant colic appears in otherwise healthy and well-developing babies as episodes of excessive paroxysmal crying, which is not helped by routine comfort measures. Colic begins at about 2 to 3 weeks of age and ends anywhere between 3 and 6 months of age. There is no laboratory test to diagnose this condition. Doctors often have to rule out all the other conditions that can make the baby cry excessively, some of which can be life-threatening.
One of the most widely used definitions of baby colic, which was proposed by Dr. Wessel back in 1954 (1) and is used by many today, states the “Rule of 3”: crying lasting longer than 3 hours per day, 3 days per week and continuing for more than 3 weeks. The crying of an infant with colic has a typical pattern described as loud, piercing, high-pitched and aversive. The crying may be accompanied by tensing of the abdominal muscles, flexing of the legs, lifting of the head, flushing of the face, clenching fingers and passing gas. The peak period of crying usually occurs in the evening. The attack may terminate when the infant is completely exhausted, or with the passage of stool or gas (2).
The estimated number of babies affected by infant colic published by different researchers varies from as low as 3% to as high as 40%. Most researchers agree the number is somewhere between 10% to 20% (3). With the current birth rate in the United States of about 4,000,000 babies a year, this translates into about 400,000 – 800,000 cases of colic a year.
Causes of Infant Colic
The cause, or causes of infant colic are still unknown. However, doctors who study colic, have reported many interesting observations:
- It is more common among the first born (4).
- It is more common among breast fed infants (5).
- Colicy babies have an increased amount of the hormone motilin in their blood, which is known to stimulate gastrointestinal tract (Motilin can cause cramping) (6).
- Babies with colic have an increased amount of serotonin by-products in the urine, suggesting an increased production of serotonin (Serotonine can also produce cramping) (7).
- Babies with colic have abnormal contractility of the gallbladder (8).
- Babies with colic have increased intestinal permeability (Incompletely digested substances may enter blood stream) (9).
- Mothers of babies with colic experience more stress and anxiety (10).
- Mothers of babies with colic are older, with higher level of education (5).
- Mothers of babies with colic are more likely to consume broccoli, cauliflower, cabbage, onions, chocolate and cow’s milk (11).
All theories that explain infant colic fall into several categories:
1. Psychological Causes of Infant Colic
Psychological, such as an abnormal interaction between mother and infant. One theory suggests that maternal anxiety is sensed by an infant, and an infant responds to such with colic, which in turn makes the mother more anxious, setting a vicious cycle. Possibly, an anxious mother actually has increased levels of yet unidentified substances in her breast milk that cause intestinal cramps in an infant. A combination of an increased level of maternal anxiety and more frequent breast feedings among infants with colic points toward this theory.
2. Gastrointestinal Causes of Infant Colic
Hyperactivity, or immaturity of gastrointestinal tract response to either external, or internal stimulation, intestinal spasms, or excessive production of gas (12, 13, 14). There is a substantial amount of evidence, such as increased level of motilin, decreased gall bladder activity, and increased hydrogen production, indicating, abnormal function of gastrointestinal tract in babies with colic. Gastroesophageal (GE) reflux (R) also has been proposed as a potential cause of infant colic. It is true that GER can make the baby cry excessively and imitate colic, however, GER can be successfully treated with either dietary changes, or appropriate anti-reflux medicine. GER is a condition in its own right and should not be confused, or mixed with infant colic.
3. Allergic Disorders Contributing to Baby Colic
Allergic reactions, such as reaction to cow’s milk, or other food constituents consumed either by an infant, or a mother. There is indirect evidence that some infants may suffer from milk protein allergies, or lactose intolerance, or even from general sensitivity to foods consumed by nursing mothers. However, only a minority of babies with colic respond to hypoallergenic formulas.
4. Misbalance between serotonin and melatonin production.
According to this intriguing theory, infants with colic have increased production of serotonin, which is not opposed by production of melatonin (15). Production of melatonin normally starts at approximately three months of age, when colic frequently ends. Since allergies may be responsible for increased production of serotonin, there may be a link between the last two theories.
Many different theories try to explain infant colic. However, none of these theories explains all cases of infant colic and no theory takes into account all the known facts of infant colic. It is likely that baby colic is a multifactorial condition, which has a similar presentation, but is produced by different causes in different infants.