Children who do not have a regular bedtime are more likely to suffer behavioural problems, according to new research.
Erratic bedtimes can cause a similar effect to jet lag and the longer youngsters go without regular bedtimes, the greater the impact on their behaviour, experts found.
They believe going to bed at different times could disrupt natural body rhythms and cause sleep deprivation. In turn, this undermines the way the brain matures and the ability to regulate some behaviours.
The study on more than 10,000 children was carried out by experts at University College London (UCL).
The experts found that youngsters who experienced erratic bedtimes throughout childhood displayed progressively worse behaviour.
Professor Yvonne Kelly, from UCL's department of epidemiology and 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."