Chronic missed naps could put toddlers at risk for mood-related problems later in life, according to a new study led by the University of Colorado, Boulder.

The study shows toddlers between 2 and a half and 3 years old who miss only a single daily nap show more anxiety, less joy and interest, and a poorer understanding of how to solve problems, said CU-Boulder Assistant Professor Monique LeBourgeois, who led the study. The results indicate insufficient sleep alters the facial expressions of toddlers; exciting events are responded to less positively, and frustrating events are responded to more negatively, she said.

"Many young children today are not getting enough sleep, and for toddlers, daytime naps are one way of making sure their ‘sleep tanks’ are set to full each day," she said. "This study shows insufficient sleep in the form of missing a nap taxes the way toddlers express different feelings, and, over time, may shape their developing emotional brains and put them at risk for lifelong, mood-related problems."

LeBourgeois and her colleagues assessed the emotional expressions of healthy, nap-deprived toddlers 1 hour after their normal nap time, and tested them again on another day following their normal nap. The study, believed to be the first to look at the experimental effects of missing sleep on the emotional responses of young children, indicates the loss of a nap—in this case in just 90 minutes—may make toddlers unable to take full advantage of exciting and interesting experiences and to adapt to new frustrations, she said.

A paper on the subject recently appeared online and will be published in an upcoming issue of the Journal of Sleep Research.