Colic affects between 10% and 30% of babies at some point. It is defined as excessive crying, > 3 hours/day, 3 days/week, for at least three weeks. However, apparently the causes of colic are unknown. The normal span of such colicky behavior is between 2 weeks to 6 months of age. However, some last longer, and many are intermittent or simply take place once or twice. Not only that, but as an extremely common phenomena, there are an amazing number of opinions and cures, which simply do not work. There are some coping tactics, but the main thing is to persevere. Some parenting behavior can potentially calm colicky behavior, and also removing certain irritants from the environment (cigarette smoke is a big one) can also help. Still, we don't know much about this, so the important thing is to not jump to conclusions as to causes and treatments. My week old son does not have colic, though could of course, and as I child I did, at least for a little while, perhaps not the 3 hours x 3 days x 3 weeks.