CPAP use linked to lower depression risk in sleep apnea, 19% vs 24% over eight years

Plenty of people prescribed a CPAP machine for sleep apnea find the mask hard to live with, and many end up wearing it for only part of the night. A French study that followed 2,712 CPAP users for about eight years found that the ones who used it for at least four hours a night were less likely to be diagnosed with depression later. The gap was modest, and the study’s own design leaves open how much of it belongs to the machine.

Researchers at Angers University Hospital, led by Julie Garrivet with Wojciech Trzepizur as senior author, drew on a sleep clinic cohort from the Pays de la Loire region of western France and linked it to national health records. Over a median follow-up of 8.45 years, 19.2% of the regular users and 24.2% of the lighter users were diagnosed with major depression. The study was published in September in the Journal of Sleep Research.

Why depression and sleep apnea are studied together

In obstructive sleep apnea, the throat closes again and again during the night, so breathing stops and starts. It is common. One widely cited estimate, from a study funded by the CPAP maker ResMed, put the total at almost 1 billion people affected worldwide, counting adults aged 30 to 69 alone. The standard treatment is continuous positive airway pressure, or CPAP: a bedside machine that blows air through a mask to hold the airway open.

People with sleep apnea are more likely to be depressed, and the French team begins from the observation that the condition is associated with major depressive disorder. What has been less clear is whether treating the apnea changes the outlook. The authors note that limited data exist regarding the impact of CPAP on new cases of depression, as opposed to symptoms in people who are already low.

Short trials have looked mainly at symptoms. A 2014 review pooled 19 randomized trials and found that CPAP improved depressive symptoms compared with control treatments, and that it helped most in the two trials with a higher burden of depression at baseline. A larger systematic review in 2019, which pooled 20 trials, confirmed a benefit of CPAP in reducing depression symptoms, though the average effect was small. Those earlier trials carried their own distortions. The 2014 reviewers pointed to a lack of blinding of patients and outcome assessors in many of them, which tends to tilt results toward a benefit, and to uneven CPAP use, which tends to hide one.

How the Angers team compared regular and occasional CPAP users

The study drew on patients prescribed CPAP for sleep apnea who had no history of psychiatric disorders, meaning no depression, bipolar disorder, psychotic illness or anxiety disorder on record. That matters, because it lets the study ask about depression that started after treatment began rather than an old illness flaring.

The researchers used each patient’s documented nightly use of the machine to split the group in two. Those with documented CPAP use of at least 4 h per night on average, 1,885 people, counted as adherent; the 827 who used it less counted as non-adherent. Four hours is a common line in this field; the SAVE trial investigators, for example, describe it as a widely used cut-off in prior studies. Depression was counted from health records. Major depression was defined by antidepressant prescription or a hospital stay for depression.

Over the follow-up, 561 (20.7%) of 2,712 patients developed major depression, about one in five. Among the lighter users it was 200 of 827, and among the regular users 361 of 1,885. After the researchers took account of age, sex, body mass index, job and social background, complaints of insomnia, and depressive symptoms measured at the start, regular use was still linked to about 17% lower risk. The authors conclude that in CPAP-treated patients free of psychiatric illness, “adherence to therapy is associated with a lower incidence” of major depression. That result sits close to the line. The statistical range around it runs from about 30% lower risk to about 1% lower, so a true effect near zero is not ruled out.

Who keeps using CPAP every night?

The comparison in this study is between people who chose, night after night, to wear the mask and people who did not. That is a different thing from a trial in which a coin decides who gets the machine.

People who keep up a demanding treatment for years often differ from those who give up in ways that matter for health on their own: steadier routines, more support at home, other healthy habits, or simply feeling better to begin with. Researchers call this the healthy adherer effect. An American Thoracic Society statement on sleep apnea and heart disease warns that comparisons of adherent and non-adherent CPAP users are subject to potential healthy adherer bias and residual confounding, the second term meaning differences the analysis could not fully measure.

The direction can also run backward. Early, unrecognized low mood can make it harder to persist with a mask every night, so some of the lighter users may already have been sliding toward depression when their use fell off. The adjustment for depressive symptoms at the start helps with that, but only for symptoms present at the beginning. The authors raise a version of this themselves. Their paper closes by asking whether non-adherent patients display vulnerability factors of their own, insomnia among them, that could raise their risk of depression whatever the machine does.

What a randomized trial found about CPAP and depression

The strongest test of the question comes from the SAVE trial, which randomly assigned 2,410 patients with co-existing moderate-severe sleep apnea and heart or blood vessel disease to CPAP or to usual care, and followed them for an average of 3.7 years. Because chance decided who got the machine, the comparison is not tilted by who chooses to persist.

CPAP treatment was associated with reduced odds of depression caseness, the point at which a questionnaire score suggests likely depression, by about a fifth compared with usual care. The benefit was larger in people who already had depressive symptoms, and it held independently of improvements in sleepiness, so it was not simply a side effect of feeling less tired.

Then comes the twist that matters for the French result. Inside the CPAP group, the SAVE investigators also compared people who used the machine more with those who used it less, and found no clear effect of CPAP adherence on depression or anxiety. In other words, being assigned CPAP helped, but hours of use did not track mood the way the Angers study’s split would suggest. The two studies differ in many ways, including patients with heart disease in SAVE and a much longer follow-up in France, so neither result cancels the other.

The Angers group’s own earlier work also tempers expectations. In a separate 2014 study of 300 patients with sleep apnea and depressive symptoms, led by co-author Frédéric Gagnadoux, average depression scores fell from 9.2 to 5.4 on the questionnaire used. Yet 41.7% still had symptoms after a year or more of CPAP. Those lingering symptoms were independently associated with persistent excessive daytime sleepiness that the treatment had not cleared.

What the CPAP and depression study leaves unanswered

Beyond the healthy adherer problem, the comparison is a single split at four hours a night. It says nothing about whether more hours went with lower risk step by step, or whether the lighter users stopped early or simply wore the mask for shorter nights.

The definition of depression is practical but blunt. It relied on prescriptions and hospital stays, so people with depression who never sought treatment were not counted at all. The patients all came from one regional cohort in western France, and all had already been diagnosed and prescribed CPAP in sleep clinics.

What the CPAP result means for people with sleep apnea

The study does not change how sleep apnea is treated, because the case for CPAP already rests on other grounds. The American Academy of Sleep Medicine gives positive airway pressure a strong recommendation for adults with sleep apnea and excessive sleepiness, and a weaker, conditional one for those with poor sleep-related quality of life or high blood pressure. The same guideline recommends that educational interventions be given when treatment starts, and suggests extra help with problems in the first weeks.

What the French study adds is a long-term observational link between regular use and fewer diagnoses of depression, consistent with trials showing CPAP can lift mood a little, though not with SAVE’s finding that hours of use made no clear difference. Some readers will be taking an antidepressant. Do not stop or change a prescribed medicine without talking to your doctor. How a person’s sleep apnea and mood are managed is decided with their doctor.

Regular CPAP users in western France were diagnosed with depression less often over eight years, but the gap was small and the comparison cannot separate the machine from the habits of the people who keep wearing it.