The study, published in the journal Pediatrics, found irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation, undermining brain maturation and the ability to regulate certain behaviors in children.
Professor Yvonne Kelly of the University College London and colleagues analyzed data from more than 10,000 children in the UK Millennium Cohort Study.
The research team collected bedtime data from parents for children when they were ages 3, 5 and 7. The researchers also collected reports from the children's mothers and teachers on behavioral problems.
As children progressed through early childhood without a regular bedtime, their behavioral 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 behavior, 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," Kelly said in a statement.
"But our findings suggest the effects are reversible. For example, children who change from not having to having regular bedtimes show improvements in their behavior."
Irregular bedtimes were most common at the age of 3, when around 1-in-5 children went to bed at varying times, but by the age of 7, more than half the children went to bed regularly between 7:30 and 8:30 p.m.