Babies usually cry almost two hours a day, and about 15 per cent of them cry for more than three hours a day. Excessive crying is most common during the first three to four months of life, after which the frequency of crying decreases. For some parents their baby's crying is a problem, while other consider it a normal phenomenon and do not become irritated. Parental tolerance of infant crying is dependent not only on its frequency or intensity, but also on the psychological characteristics of the parents, and the amount of information, household help and social support that is available to them. Crying during the first few months of life is usually attributed to "colic", even if it is not known whether the infant suffers from gastrointestinal disturbance. The recommended treatments for excessive crying include medication, vocal, vestibular or tactile stimulation, hospital admission, and changes in parent-infant interaction.