Taking stimulant medications may decrease quantity and quality of sleep for kids with attention-deficit hyperactivity disorder (ADHD), according to an analysis of existing studies.

"Some researchers note that stimulants may improve sleep, because they reduce bedtime-resistant behaviors," said lead author Katherine M. Kidwell, a psychology doctoral candidate at the University of Nebraska.

"However, our study shows that stimulant medications impair sleep in children," Kidwell told Reuters Health by email.

Her team reviewed nine studies of children or teens with ADHD who were randomly assigned to receive stimulant medication or not. All of the studies used objective measures of sleep.

The results of the individual studies sometimes contradicted each other, but in general, kids on stimulant medications took longer to fall asleep than others, and that time lengthened as the number of doses per day increased.

Groups on stimulants also tended to have shorter sleep duration and worse "sleep efficiency," the ratio of time spent asleep to the time spent in bed.

About seven percent of kids and teens have ADHD, and roughly 3.5 million kids in the U.S. take ADHD medication, the authors wrote in Pediatrics.

"In some of the studies, children received stimulants only once a day in the morning and in some studies they received medications at two or three times throughout the day," Kidwell said. "We think that when stimulants are in children's bodies close to bedtime, the stimulant keeps them from being able to fall asleep and reduces the quality of their sleep."

Children who took medications only once a day in the morning had less intense sleep problems, she said.

"Poor sleep actually exacerbates ADHD symptoms, particularly inattention," Kidwell said. "In addition to making ADHD symptoms worse, poor sleep leads to a host of other physical, cognitive, and emotional problems."

But, these are important medications for kids with ADHD, so they should not stop taking them, she said.

"Rather, physicians should consider the pros and cons, including the potential for disrupted sleep," she said. "Our study provides important information about a potential cost that should be factored in when considering prescribing a stimulant medication to children with ADHD."

Parents should talk to pediatricians about any change in their children's sleep, she said.

"Parents can help their children sleep better by encouraging good sleep habits, bedtime routines, and being consistent," she said. "Parents can seek out psychologists and pediatricians who are trained in treating sleep problems with behavioral solutions to alleviate the adverse effects on sleep."

SOURCE: http://bit.ly/1MArDHQ Pediatrics, online November 23, 2015.