Looking to help a troubled child? Then help him to sleep. This was the wisdom of Shakespeare, who called sleep the “balm of hurt minds", and it’s the message re-emerging from recent research, too.

It has been known for some time that children with stressful family lives often battle with emotional and academic problems. Now researchers are discovering that sleep might be a link between problems at home and problems at school. Stressed out kids don’t sleep well. And tired kids have a hard time concentrating and controlling their behavior.

Mona El-Sheikh and her US colleagues in the College of Human Sciences at Auburn University, Alabama, tracked the sleep habits of 166 eight- and nine-year-olds, asking them about the pattern of their nights and monitoring their behavior with actigraphs, which electronically measure sleep. They collected information about the children’s emotional well-being and also their scores on standardized achievement tests.

They found that children living with parents who fight a lot do not sleep as much or as well as children in less troubled households. Poor sleep, in turn, was related to lower achievement scores. They also found that the effects of disrupted sleep on achievement were more pronounced among African American children and poor children – although the reasons for them being more vulnerable are unclear.

The authors suggest that poor sleep might help to explain the troubling achievement gap between poor and well-off children and between European American and African American children. Additionally helping children (and perhaps their parents) to sleep better might go a long way toward resolving all types of problems.

Shakespeare's meditation on sleep goes on to describe it as "chief nourisher in life's feast" similarly prefiguring work at the University of Michigan Center for Human Growth and Development, where researchers have evidence that children who sleep more may run a lower risk of becoming obese.

Children aged eight or nine who do not sleep more than ten hours a night have been found to be more likely to be obese three years later, irrespective of their weight at the outset.

This study, led by Julie Lumeng, included 785 children from ten US cities. Of the those who slept fewer than nine hours and 45 minutes a night in third grade, some twenty percent were obese by the time they were in sixth grade, compared to about 12 percent of children whose nights in third grade had been longer.

Parents were asked “How much sleep does your child get each day (including naps)?” Children's height and weight were measured. The link between hours of sleep in third grade and obesity in sixth grade persisted even when certain other risk factors for becoming obese were taken into account: for example, maternal education, race, the quality of the home environment and parenting skills.

Lumeng and her team suggest three reasons why sleep may influence weight: children who do not get enough sleep are more likely to be less active during the day; tired children are more irritable and may eat more high-calorie food to regulate their mood; and lack of sleep possibly influences fat metabolism.

In relation to the last of the three, there is some evidence that adults who do not sleep enough produce more of a hormone called ghrelin, which creates a sensation of hunger, and less leptin, a hormone that tells you that you are full.

The study makes several simple recommendations: sticking to regular bedtimes and wake times, removing TVs from bedrooms and doing away with extremely early school start times.

• On Thursday What new UK research has to say about the connection between inter-parental conflict at home and greater risk of underachieving at school.

Summaries of “Child Emotional Insecurity and Academic Achievement: The Role of Sleep Disruptions” by Mona El-Sheikh, Joseph A Buckhalt, Peggy S. Keller, E. Mark Cummings, and Christine Acebo in Journal of Family Psychology, Volume 21(1), March 2007, pp 29–38
and "Shorter Sleep Duration Is Associated With Increased Risk for Being Overweight at Ages 9 to 12 Years" by Julie C. Lumeng, Deepak Somashekar, Danielle Appugliese, Niko Kaciroti, Robert F. Corwyn and Robert H. Bradley in Pediatrics Vol. 120 No. 5 November 2007, pp 1020-1029.