The cause or causes of colic are unknown, but some researchers think that indigestion or wind may play a significant role.
Other researchers believe that babies with colic may, for a few weeks while their gut is maturing, be sensitive to certain substances that are found in breast or formula milk, such as lactose (a natural sugar) or molecules found in cows' milk. It is thought that these substances may be passed on to the baby through breastfeeding. However, there is little evidence to support these theories.
Another theory suggests that some babies may be more emotionally sensitive than others, and have problems "turning off" their crying response.
Smoking
It is known that women who smoke during pregnancy double their chances of having a baby who develops colic.
This may be because smoking causes a rise in the levels of a hormone called motilin during pregnancy. Increased levels of motilin may lead to symptoms of indigestion and colic shortly after birth.
