What do you think of when you hear about a tired child? Probably a little one who is emotionally fragile and prone to becoming upset over small disappointments or setbacks. Sleep's restorative abilities are well known to parents, but, for some reason, too few parents take the importance of adequate sleep seriously enough.

Sleep is an important time for the reprocessing of emotional experiences that have occurred when awake and forming memories about the events of the day. This processing helps reset the emotional reactivity of the individual, such that the stresses and distresses of the day do not overwhelm emotional functioning into the next day. That's why one research team called it a form of overnight therapy.

“Parents…need to think about sleep as an essential component of overall health in the same way they do nutrition, dental hygiene and physical activity.”

Just as a lack of sleep makes children less able to learn and more likely to become overweight, it can also make it much harder for children to handle their emotions, according to a recent study. And a lack of emotional control can set the stage for a wide variety of emotional issues.

Researchers restricted sleep in 50 children, ages 7-11 years. Then they looked at how well these children could appraise, express, regulate and later recall emotional experiences, as compared with a group of well-rested peers. How would they feel and what would they enjoy? Would they remember having fun? Being happy? Feeling content? How would they describe their activities and interactions?

After just two nights of inadequate sleep, the tired children were not as happy. They experienced less pleasure from enjoyable experiences, forgot more of the pleasurable experiences that they had had, and remembered things in a more negative light than the control group of rested children, the University of Houston researchers found.

Not only did tired kids have fewer positive feelings, they also had more negative emotions than their peers. The researchers concluded that lack of rest disrupts emotional processes, including one's ability to take pleasure in and remember enjoyable experiences. This can set the stage for mental health issues both immediately and in the long-term.

“Healthy sleep is critical for children's psychological well-being,” researcher Candace Alfano said in a university press release. “Continually experiencing inadequate sleep can eventually lead to depression, anxiety and other types of emotional problems. Parents, therefore, need to think about sleep as an essential component of overall health in the same way they do nutrition, dental hygiene and physical activity. If your child has problems waking up in the morning or is sleepy during the day, then their nighttime sleep is probably inadequate. This can happen for several reasons, such as a bedtime that is too late, non-restful sleep during the night or an inconsistent sleep schedule.”

The emotional vulnerability a lack of sleep brings on is not limited to children, of course. In earlier research the study's authors found that when people were tired, they were less likely to seek out pleasurable experiences and find opportunities for positive and rewarding pursuits, decreasing a person's quality of life and increasing the risk for depression.

In this way poor sleep affects interpersonal relationships because it impairs one's ability to read non-verbal cues and to accurately interpret others' behaviors. These impaired social skills increase isolation, decrease satisfaction and confidence in social situations and similarly detract from quality of life. When sleep problems begin in childhood, these deficits have the potential to create life-long mental health issues.

The authors conclude that adequate sleep is an essential building block for mental health and social functioning. They stress that many poor sleep habits, some mental health issues and maladaptive behaviors have their origins in childhood.

Parents who feel their children are getting too little sleep should not hesitate to identify the problem both to themselves and their pediatricians. It may take a few adjustments but there are many strategies — from establishing bedtime routines to earlier bedtimes — that can help children with poor sleep behaviors get the rest they need.

The study is published in Sleep Medicine Reviews.