Researchers from UCL have found that children with irregular bedtimes are more likely to have behavioural difficulties.
The study, which is published in the journal Pediatrics, found that irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation, undermining brain maturation and the ability to regulate certain behaviours.
Professor Yvonne Kelly (UCL Epidemiology & Public Health), said: "Not having fixed bedtimes, accompanied by a constant sense of flux, induces a state of body and mind akin to jet lag and this matters for healthy development and daily functioning."
"We know that early child development has profound influences on health and wellbeing across the life course. It follows that disruptions to sleep, especially if they occur at key times in development, could have important lifelong impacts on health."
Analysing data from more than 10,000 children in the UK Millennium Cohort Study, the team collected bedtime data at three, five and seven years, as well as incorporating reports from the children's mothers and teachers on behavioral problems.
The study found a clear clinical and statistically significant link between bedtimes and behavior as irregular bedtimes affected children's behavior by disrupting circadian rhythms, leading to sleep deprivation that affects the developing brain.
As children progressed through early childhood without a regular bedtime, their behavioural scores - which included hyperactivity, conduct problems, problems with peers and emotional difficulties - worsened. However, children who switched to a more regular bedtime had clear improvements in their behaviour.
Professor Kelly said: "What we've shown is that these effects build up incrementally over childhood, so that children who always had irregular bedtimes were worse off than those children who did have a regular bedtime at one or two of the ages when they were surveyed.