Insomnia has long been known as a key feature of serious mental illnesses such as depression, but new research from the University of Pennsylvania also links it to increased risk of suicide.

Sleep scientists evaluated a group of nearly 500 people with insomnia. They found that among those who had thought about ending their lives, the risk went up significantly depending on how little they slept. Each additional hour of sleep decreased the likelihood of suicidal thoughts.

They also examined data from a major national survey, and compared people with insomnia and those who sleep well. They found an increased risk for suicide and suicidal thoughts among those who had the sleep problems.

"These studies just go to show the important connection between sleep and mental health," said Dr. Michael Grandner, a psychologist and researcher with Penn's Behavioral Sleep Medicine Program. "Making sleep a priority is so important," he added.

Many family physicians do not ask their patients about sleep, Grandner said, but they should. Patients also should bring up sleep issues with their doctors. He adds that people should value sleep as a crucial part of their overall health and well-being.

The studies suggest that treating insomnia could be another tool in the fight against suicide, he said.

"These studies can't yet tell us that you can change suicide risk by changing sleep, but it is highly likely that improving your sleep will improve a lot of different aspects of your life and well-being," he said.

Grandner says that an approach known as cognitive behavioral therapy has been successful in treating insomnia.