What Causes Colic In Babies?

Colic is one of the most exhausting things a new parent can face. A healthy, well-fed baby who screams for hours every evening, often at the same time each day, can leave you feeling helpless and second-guessing everything you are doing. The honest answer is that no single cause has been identified. Colic is best understood as a set of behaviors — intense, prolonged crying in an otherwise healthy infant — rather than one disease with one trigger. Researchers have proposed several explanations, and most likely, different babies cry this way for different reasons.

What Is Colic, Exactly?

Colic describes repeated episodes of crying for more than three hours a day, more than three days a week, for more than three weeks, in a baby who is otherwise healthy and growing normally. That definition, often called the “rule of three,” was described by pediatrician Morris Wessel in 1954 and is still widely used in research and clinical practice.

Two things about that definition matter. First, it is a description, not a diagnosis of a specific underlying problem. Second, it is based on how much and how often a baby cries — not on why. That is a big part of why the cause has been so hard to pin down.

Colic typically starts in the first few weeks of life, peaks around six to eight weeks, and improves on its own by around three to four months. The timing is fairly consistent across cultures and feeding methods, which suggests something about early infant development is involved rather than something a parent is doing wrong.

It is also worth separating colic from ordinary evening fussiness. All babies have a period of increased crying in the late afternoon and evening during the first months. Colic is the extreme end of that range.

What Causes Colic In Babies?

No single cause has been confirmed. What researchers have found is a cluster of plausible contributors, and the evidence for each varies in strength. Here is where the science currently stands.

An Immature Nervous System

This is one of the most widely accepted explanations. Newborns are born with a nervous system that is still developing. Their ability to regulate arousal, calm themselves, and shift between states like alert and sleepy is limited. Some researchers describe colic as a kind of “overshoot” of normal crying behavior while those regulatory systems mature.

This fits the timeline well. Colic peaks and then fades as the brain and gut mature, roughly in parallel. It also helps explain why colic occurs across cultures, feeding methods, and caregiving styles — it appears to be a developmental phase, not a reaction to a specific environment.

Gut and Digestion Factors

The gut is the most studied area, and also the most misunderstood. Several findings are worth knowing.

• Gut bacteria differences. Some studies have found that infants with colic have different patterns of gut bacteria than infants without it. Whether this is a cause or a consequence of prolonged crying is not clear.
• Gas and trapped air. Swallowed air and immature digestion can cause discomfort, but gas alone does not explain why colic follows such a predictable daily pattern. Gas is often a symptom, not the root cause.
• Lactose and carbohydrate digestion. Some infants may have temporary difficulty digesting lactose, the sugar in milk. This is more common after a bout of gastroenteritis than in typical colic.
• Gut hormones. Some research has looked at hormones that influence gut movement, such as motilin, and found differences in infants with colic. The findings are not consistent enough to be considered settled.

The gut is clearly involved in many cases. But calling colic “a stomach problem” oversimplifies what is likely a mix of neurological and digestive factors.

Feeding and Milk Protein Sensitivity

A small subset of infants with colic symptoms turn out to have a sensitivity to cow’s milk protein. This is a genuine immune reaction to proteins in cow’s milk, and it can cause crying, vomiting, diarrhea, blood in the stool, or poor weight gain.

Most babies with colic do not have this sensitivity. But when symptoms are severe, persistent, or come with those other signs, a clinician may consider it. This is a medical question, not something to self-diagnose or treat by switching formulas on your own.

Parenting and Environment

Parenting style does not cause colic. This has been studied, and the old idea that colic was a result of parental anxiety or poor bonding has not held up. Colic occurs in babies with attentive, loving parents across all kinds of households.

What is true is that colic can strain parents. The crying is relentless, and no amount of holding, rocking, or feeding may stop it. That strain is real, and it is not a sign you are doing something wrong.

Does Colic Mean Something Is Wrong With My Baby?

In most cases, no. Colic is defined by crying in a baby who is otherwise healthy — feeding well, gaining weight, and having normal stools and urine output. The crying itself is the problem, not a sign of a hidden illness.

That said, some conditions can look like colic. A clinician should evaluate symptoms that do not fit the typical pattern. Signs that warrant a medical visit include:

• Crying that starts suddenly and is much more intense than usual
• Vomiting that is forceful or green
• Blood in the stool, or stools that are very loose or very hard
• Poor weight gain or weight loss
• Fewer wet diapers than expected
• Fever
• A baby who seems unusually sleepy, floppy, or hard to wake
• Crying that continues past four months or gets worse instead of better

These signs do not mean something is definitely wrong. They mean a clinician should take a look. Trust your sense of when something seems off.

Why Does Colic Follow a Schedule?

The evening clustering is one of colic’s most striking features, and it points toward a developmental explanation. Around the same time each day, many newborns have a longer stretch of fussiness. In babies with colic, that stretch becomes extreme.

Some researchers think this reflects the slow development of the systems that regulate sleep, arousal, and the body’s daily rhythms. Newborns do not yet have a mature circadian rhythm — the internal clock that organizes sleep and wake cycles. As that clock matures over the first few months, the evening crying tends to fade.

This is a reasonable explanation supported by the timing, but it is not proven as the direct cause. Colic research has a recurring problem: many findings describe what is different about babies with colic, without proving that difference caused the crying.

What Actually Helps With Colic?

There is no treatment that reliably stops colic, because there is no single cause to target. What helps most is managing the crying and supporting the parents through it.

Approaches with some evidence or common clinical use include:

• Responsive soothing. Holding, rocking, swaddling, and gentle motion can calm some babies. They do not cure colic, but they reduce distress in the moment.
• Reducing swallowed air. Burping well and feeding in a calm position may reduce gas discomfort, though this rarely resolves colic on its own.
• Taking breaks. Handing the baby to a trusted caregiver for a short time when you are overwhelmed is a safety measure, not a failure.
• Talking to your pediatrician. A clinician can check for the conditions that mimic colic and discuss whether a trial of a different formula or a change in the breastfeeding parent’s diet is worth considering.

Be cautious with products marketed to “cure” colic. Simethicone drops, gripe water, and herbal remedies are widely sold, but the evidence that they resolve colic is weak. Some herbal preparations have been linked to safety concerns in infants. Talk to a clinician before giving a baby anything beyond breast milk or formula.

Probiotics have been studied for colic, and results have been mixed. Some trials in breastfed infants suggest a possible benefit with certain strains, while others show no clear effect. No probiotic is established as a standard treatment for colic.

The Bottom Line for Parents

Colic has no single known cause. The best-supported explanation is that it reflects an immature nervous system and digestive tract, with gut bacteria, feeding factors, and developmental timing playing supporting roles in different babies. It is not caused by parenting.

The hard part is that colic is a phase you largely have to get through. It improves on its own, usually by three to four months. What you can control is how you and your baby are supported during that stretch. If the crying feels unmanageable, or if you notice any of the warning signs above, reach out to your pediatrician. You do not have to figure this out alone.