(Reuters Health) – Soldiers who experience sleep problems during basic combat training may be more likely to struggle with psychological distress, attention difficulties, and anger issues during their entry into the military, a recent study suggests.

“These results show that it would probably be useful to check in with new soldiers over time because sleep problems can be a signal that a soldier is encountering difficulties,” said Amanda Adrian, lead author of the study and a research psychologist at the Center for Military Psychiatry and Neuroscience at Walter Reed Army Institute of Research in Silver Spring, Maryland.

“Addressing sleep problems early on should help set soldiers up for success as they transition into their next unit of assignment,” she said by email.

Adrian and colleagues surveyed 1,577 soldiers during the 10-week basic combat training at weeks 1, 3, 6, and 9 to see whether they were experiencing sleep problems or any issues with mood disorders, anger, or attention.

About 61% of the soldiers in the study never had a sleep problem. Another 13% started out with sleep issues but recovered during training, while 20% developed sleep problems during training and about 7% had chronic sleep issues throughout the study.

Compared to soldiers who never had sleep problems, those who recovered from initial sleep problems started out with higher psychological distress, anger reactions and attention problems but steadily improved throughout training, the study found.

Those who developed sleep problems during training or had chronic sleep problems had slower improvements in psychological distress and a decline in attention throughout the study. And the group with chronic sleep problems also had increasing anger issues throughout the study.

Sleep problems have long been linked to poor mental health, emotional regulation, cognitive function, and job performance, the researchers note in Sleep Health. But little is known about how sleep problems among people in high-risk occupations like firefighting and policing might impact their job performance, or the safety of people they're charged with protecting.

The current study wasn't a controlled experiment, so it can't prove sleep problems caused issues with mood, attention or anger reactions. Another limitation is that researchers relied on soldiers to accurately recall and report on any problems with sleep, attention, anger or mood. And the study didn't assess sleep duration or underlying factors that might lead some soldiers to develop sleep problems while others did not.

“There is evidence that both reduced hours of sleep and poor quality of sleep are associated with adverse mental health and cognitive functioning,” said Sanford Nidich, director of the Center for Social and Emotional Health at Maharishi University of Management Research Institute in Fairfield, Iowa.

“The results of this current study on soldiers undergoing basic combat training provide further support on the connection between sleep quality and mental health, especially in the areas of anger reaction and attention,” Nidich, who wasn't involved in the study, said by email. “While it is difficult to conclusively determine cause-and-effect from this study, it is clear that both quality of sleep as well as adverse mental health issues need to be addressed in terms of prevention and treatment.”

Military personnel, like civilian adults, need approximately 8 hours of sleep per night for optimal job performance, said Dr. Hohui Wang, a psychiatry researcher at the University of California San Francisco who wasn't involved in the study.

“Persistent insomnia negatively impacts cardiometabolic and neurocognitive functions, and is associated with future development of PTSD, depression and anxiety,” Wang said by email.