Forget what the toddler taming textbooks recommend, according to a new US study into early childhood sleep patterns, toddlers may be better at choosing their own bedtime than their parents.

Researchers from the University of Colorado, Boulder, found that a major cause of broken sleep or difficulty nodding off without a fight is that many toddlers are being put to bed before their internal body clock is ready.

The body clock, also known as one’s circadian rhythms, is a system governed by the hormone melatonin, which naturally increases during the evening to put the body in an optimum state for sleeping.

The study aimed to find out whether parents selecting a bedtime that was out of sync with their child’s circadian system could lead to nighttime settling difficulties such as bedtime resistance and sleep-onset delay.

Sleep and settling difficulties occur in about 25 percent of young children, they noted, and are often associated with attention, behavioral, and emotional problems.

The researchers followed a group of toddlers aged between 30 and 36 months, and measured their melatonin levels at various intervals around bedtime for six nights. They recorded the time it took them to fall asleep as well as their behaviour around bedtime.

The rise and fall of melatonin levels is linked to factors such as the amount of light and a person’s physical make up – so the time of evening when melatonin is at the right level to promote sleep will vary from child to child, they found.

The study findings, published in the Mind, Brain and Education journal, showed that melatonin levels tended to rise at around 7.40pm in the evening and if parents then waited half an hour to put their children to bed, the child was typically asleep within 30 minutes.

However, if children with later lifts in melatonin levels were put to bed at this time, they took longer to go to sleep and were more likely to be unsettled.

A premature bedtime might make toddlers resist bedtime, throw tantrums and resort to 'curtain calls' – constantly getting out of bed or coming into their parents' bedroom – the scientists warned.

Associate professor and physiologist Monique K. LeBourgeois, who led the study, reported that “Toddlers with longer intervals between the onset of nightly melatonin release and their subsequent bedtimes were shown to fall asleep more quickly and had decreased bedtime resistance as reported by their parents.”

Put simply, the more tired toddlers are when they are put to bed, the more likely they are to sleep quickly and soundly.

LeBourgeois added: “For these toddlers, lying in bed awake for such a long time can lead to the association of bed with arousal, not sleep.

“This type of response may increase children's lifelong risk for insomnia over time.”

The scientists didn’t, however, offer any suggestions as to how parents will be able to tell when exactly their toddler’s melatonin levels are high enough for easy settling or sleeping.

Tell us below… Do you think letting your toddler 'tell you' when they are ready for bed is a good idea? What works best for you when getting your baby or toddler to sleep?