Sleep problems are a well known symptom of depression, but a new study also raises the possibility that they could cause depression as well.
Researchers examined a sample of nearly 2,000 Australian men between the ages of 35 and 83 and found that those with excessive daytime sleepiness were 10 percent more likely to be depressed compared to those without. According to the researchers from the University of Adelaide and the Adelaide Institute for Sleep Health, the relationship held up even after taking other risk factors into account.
Of the men examined for the study, none of them had been diagnosed with obstructive sleep apnea when they began, but 857 of them were assessed for the condition after joining. Those who were found to have it were 2.1 times more likely to be depressed than those who didn't have the sleep disorder.
Some of the men had severe sleep apnea and excessive daytime sleepiness. Researchers found that the men in this group were 4.2 times more likely to be depressed compared with men who had no sleep issues whatsoever. Those who suffered from both conditions were also 3.5 times more likely to be depressed than men with only one of them.
The men were evaluated on two separate occasions for depression. Once at the beginning of the study and the second test coming about five years after the first. That allowed for the researchers to se if the sleep problems could be linked to a recent diagnosis of depression.
The men who had severe sleep apnea that was found during the study were 2.9 times more likely to become depressed during those five years.
The study didn't allow for researchers to determine if sleep problems boosted the men's risk for depression. It is possible the reverse is actually true, or that a third factor makes people more likely to be depressed and have trouble sleeping.
While the link between sleep and depression is still hazy at best, the results provide actionable information for doctors, the study authors concluded. After patients are diagnosed with depression, they should also be screened for sleep apnea, even if they don't seem sleepy, the researchers said. While it is not clear how sleep is linked to depression, it is obvious that those who are depressed often have sleep problems that also need to be addressed by physicians as a part of treatment for patients with depression.
The results of the study were presented at the American Thoracic Society's 2015 International Conference in Denver, CO this week.
