It is an age old dilemma for parents - should they attend to a baby who wakes in the night and cries or leave them to ‘cry it out'? A new study suggests that most infants over the age of six months should be left to cry.

According to US psychologist, Prof Marsha Weinraub, who specialises in child development, waking in the night is the most common concern that parents report to doctors in relation to their babies.

She noted that by six months of age, ‘most babies sleep through the night, awakening their mothers only about once per week. However, not all children follow this pattern of development'.

She and her team analysed the sleeping patterns of over 1,200 infants aged between six and 36 months. They found two distinct groups - sleepers and transitional sleepers.

By six months of age, two in three babies were sleepers, waking once a week or less, while one in three were transitional, waking seven nights per week at six months, falling to two nights per week at 15 months and one night per week at 24 months.

The study showed that the majority of babies who woke in the night were boys. These babies also tended to display a more difficult temperament, such as irritability. They were also more likely to be breastfed. The mothers meanwhile were more likely to be depressed.

Prof Weinraub said that the findings highlight the importance of allowing babies to learn how to fall asleep by themselves.

"When mothers tune in to these night time awakenings and/or if a baby is in the habit of falling asleep during breastfeeding, then he or she may not be learning how to self-soothe, something that is critical for regular sleep," she explained.

She also suggested that if a mother is depressed, she may have been depressed during pregnancy, which may have affected the neural development and subsequent sleeping behaviour of the child. However, she also acknowledged that sleep deprivation will worsen maternal depression.

"Because the mothers in our study described infants with many awakenings per week as creating problems for themselves and other family members, parents might be encouraged to establish more nuanced and carefully targeted routines to help babies with self-soothing and to seek occasional respite.

"The best advice is to put infants to bed at a regular time every night, allow them to fall asleep on their own and resist the urge to respond right away to awakenings," she said.

Details of these findings are published in the journal, Developmental Psychology.