It is normal for infants to wake and feed at night during the first few months, especially when breast fed. Indeed, such behaviour is adaptive, since it secures the nutrition necessary for physical development and brain growth, and is particularly important for vulnerable infants.1 These adaptive aspects of frequent night waking become increasingly less important as the infant grows, and by around 6 months of age infants are usually able to sustain prolonged periods of sleep when they do not wake to feed, without any costs in terms of their physical development. Nevertheless, a substantial proportion of infants aged 6 months and older may wake and then have difficulty settling back to sleep without their parents’ active intervention (see Stein and Barnes2 for a review). In fact, it is this settling difficulty, rather than the awakening per se, that is the key factor distinguishing between infants with and without sleep problems.3^–5 Although there are cultural variations, daytime demands on parents in many societies are such that getting the infant to sleep throughout the night without the need to actively intervene is often a high priority. Indeed, it is well-established that sleep difficulties in infants, and the associated reduction in parental sleep, are associated with impairments in family relationships, lower parental mood and poorer daytime functioning3 6 7; and when infant sleep problems are marked, they are predictive of subsequent child behaviour problems.8^–10

The development of infant sleeping habits is a complex matter: individual differences in infant state-regulation capacities, and in the ability to shut out stimulation, can directly affect the ease with which the infant can slip smoothly into …