Want to raise successful kids? Give them regular bedtimes.

As a parent, I know that bedtime can be a struggle, especially with younger kids. But it's backed by science: Kids who have regular bedtimes at young ages wind up with better math skills, better reading skills, and better spatial awareness--all of which can lead to a cascade of positive results.

The study is exactly the kind of research I include in my free ebook, How to Raise Successful Kids, which you can download here. It comes to us from the ESRC International Centre For Lifecourse Studies in Society and Health in England. 

Beginning with a trove of data related to 11,000 7-year-old children in the UK, researchers correlated how well they did on assessment tests with their childhood sleep schedules -- at age 3, age 5, and age 7.

They found, perhaps unsurprisingly, that irregular bedtimes were most common among 3-year-olds. As kids got a bit older, their sleep schedules generally became more consistent, but the ones whose bedtimes remained volatile were more likely to do poorly on the reading, math and spatial awareness assessments.

Besides simply being tired, the researchers theorized perhaps that volatility in body rhythms and sleep deprivation, ultimately "undermin[es] the plasticity of the brain and the ability to acquire and retain information," according to a statement from University College London, where their research center is located.

Of course, none of this is in a vacuum. Just last week,  I reported on a study out of the University of Michigan that showed that among adults -- neophyte doctors who were interning in hospitals and who agreed to record their moods and their sleep patterns -- bedtimes had a strong correlative relationship with moods and depression symptoms.

Those who went to bed at the same time felt better and showed fewer symptoms of depression. 

Interestingly, it didn't matter if they slept in during the morning or tried to make up for lack of sleep on the weekends. It was the structure of sleep patterns that predicted moods, as opposed to the amount or quality of sleep.

I came across this sleep study recently after reading about the British Birth Cohorts, which are probably the most comprehensive longitudinal studies in human history -- and the source of the data studied by the researchers in this case.

Starting in 1946, British researchers have tracked more than 70,000 children from birth, noting everything from the amount of money that their parents spent on nursery items when they were born, through their income and wealth at age 30, and beyond.

As Helen Pearson, who wrote a book about the cohorts points out, there have been at least 6,000 research studies as a result of the cohorts. Besides the original group, born in 1946, there have been additional research efforts focusing on kids born in 1958, 1970, and 2000.

The children in this sleep study were all part of the Millennium Cohort Study, which tracked children born in the United Kingdom starting in 2000.

Of course, we have to keep in mind our old friend, "correlation vs. causation." It might well be that kids with irregular sleep times are more likely to share another common characteristic, or maybe several, that lead them to perform less well on these assessments.

Maybe kids with irregular bedtimes are also less likely to get nutritious meals on a regular basis, or to have a clean, comfortable place to do homework. Or maybe it's just that parents who insist on regular bedtimes are also likely to insist on another factor we've seen leading to children's success: making them do chores.

There comes a time in most successful people's lives when their children's long-term success begins to become more important than their own. So the next time you're going through a bit of a bedtime battle with your kids, maybe keep this study in mind.

My free ebook is called How to Raise Successful Kids. It's in its 7th edition, and you can download it here.