Sleep apnea, a condition that causes sleepers to stop breathing and gasp for air, may be linked to depression, according to a new study.  Men with sleep apnea are twice as likely to be depressed and the emotional impact for women is even greater. Female sleep apnea sufferers are five times as likely to show signs of depression compared to normal sleepers, researchers reported

Sleep apnea often persists undiagnosed. Researchers relied on self reporting and more than 80 percent of people who reported classic sleep apnea symptoms such as snorting or gasping for breath in their sleep were never officially diagnosed.

People who reported sleep apnea symptoms without an official diagnosis were three times more likely to exhibit symptoms of depression, such as hopelessness, feeling like a failure and poor appetite, according to the study.

Mental health professionals often ask about certain sleep problems such as unrefreshing sleep and insomnia, but likely do not realize that [sleep apnea] may have an impact on their patients' mental health. the researchers, led by Dr. Anne Wheaton, an epidemiologist with the Centers for Disease Control and Prevention, wrote in the study.

Over 100 million people worldwide have sleep apnea, many of whom remain undiagnosed according to the World Health Organization. Undiagnosed sleep apnea adds $3.4 billion a year to medical costs, according to a 1999 study.

More research is needed to determine whether treating sleep apnea will alleviate depression symptoms, the researchers wrote.

Sleep apnea is most commonly treated with a continuous positive airway pressure, also known as CPAP, machine. The machine fits over the users face like a mask and blows air into the throat to keep the airway open, allowing the user to sleep without having to wake up to breath. Surgery can also be performed to increase the size of the airway, but is very painful, requires months of recovery and slightly changes facial appearance.

The journal Sleep will publish the study in April.

This study underscores the seriousness of sleep apnea, a condition that is already linked to a multitude of other health issues.

People with severe sleep apnea are at a higher risk of stroke, according to research presented at the American Stroke Association's International Stroke Conference in February. Researchers conducted a sleep study on 61 patients who suffered a stroke without any symptoms, known as a silent stroke, and found 91 percent of them had sleep apnea.

We found a surprisingly high frequency of sleep apnea in patients with stroke that underlines its clinical relevance as a stroke risk factor, Jessica Kepplinger, lead researcher and research fellow at the Dresden University Stroke Center's Department of Neurology, said in a statement.

Sleep apnea may also be a risk factor for dementia in women, according to a study published in the Journal of the American Medical Association. Researchers studied 105 women with an average age of 82 who were diagnosed with sleep apnea but otherwise healthy. Five years later, 45 percent of the women with sleep apnea had developed some form of dementia. After adjusting for factors such as age, race and smoking status, researchers concluded that people with sleep apnea are 85 percent more likely to develop dementia.

Sleep apnea can also put a damper on your sex life. Researchers compared 80 women with sleep apnea to 240 women without the condition and found women with sleep apnea had a lower libido and more instances of sexual dysfunction, according to a study published in the Journal of Sexual Medicine.

Gasping for air can cause erectile dysfunction as well, according to a study published in the American Journal of Respiratory and Critical Care Medicine. Mice that underwent intermittent periods with a lack of oxygen, much like people with sleep apnea do, had a lower libido and developed erectile dysfunction. The mice did not fully recover six months after the study concluded, leading researchers to conclude sleep apnea can cause long-term damage even once it is treated.