Experiencing breathing problems during sleep may raise your risk of depression, a new study suggests.

Women with sleep apnea, in which breathing becomes shallow or pauses briefly during sleep, were 5.2 times as likely to have depression compared with women without the condition. Men with sleep apnea were 2.4 times as likely to have depression as men without the condition, according to the study from researchers at the Centers for Disease Control and Prevention (CDC).

Participants in the study who had other breathing problems during sleep also had an increased risk of depression. However, the researchers found no increased likelihood of depression among people who snore.

"Snorting, gasping or stopping breathing while asleep was associated with nearly all depression symptoms, including feeling hopeless and feeling like a failure," said study researcher Anne Wheaton, an epidemiologist with the CDC. "We expected persons with sleep-disordered breathing to report trouble sleeping or sleeping too much, or feeling tired and having little energy, but not the other symptoms."

Both depression and breathing problems during sleep are common, and both are underdiagnosed, the researchers wrote. Screening people who have for one disorder for the other could lead to better diagnosis and treatments, they said.

The researchers took into account other factors that might influence the results, such as age, sex and weight. The results are in line with those of the other studies, the researchers said.

The study found an association, not a cause-and-effect link. However, the researchers wrote that evidence from other research suggests that breathing problems during sleep may contribute to the development of depression. For example, one previous study found a link between the severity of breathing problems during sleep and the odds of later developing depression. And other studies have shown that people who received treatment for sleep apnea showed improvement in their depression.
"Mental health professionals often ask about certain sleep problems, such as unrefreshing sleep and insomnia, but likely do not realize that [breathing problems during sleep] may have an impact on their patients' mental health," the researchers wrote in their conclusion.

Although exactly how the link might work is unclear, it could partly be explained by the fact that people with breathing problems experience sleep that is fragmented, or may have low levels of oxygen in the blood during sleep.

The researchers used data collected from 9,714 adults who participated in the National Health and Nutrition Examination Survey, which is an ongoing study conducted by the CDC.

Participants were considered to have depression based on their answers to a questionnaire asking about how often they experienced symptoms of depression.

Six percent of men and 3 percent of women in the study reported having physician-diagnosed sleep apnea.

The study was limited in that participants' depression and sleep problems were measured at only one point in time, and in that it relied on self-reported symptoms. People may not be aware they have breathing problems during sleep, and there was no information about whether participants were being treated for depression.

The study is published in the April issue of the journal Sleep.