People who prefer to sleep late in the morning and stay up late at night have a higher-than-average risk of depression—a link that may be especially risky for people who have type 2 diabetes, since the two diseases are already so intertwined.
The new study, which was presented this week at the Endocrine Society’s annual meeting in Orlando and has not yet been published in a peer-reviewed journal, analyzed questionnaires about mood, sleep quality, and time preferences from 476 people in Chicago and Thailand who have diabetes. (The researchers wanted to include two different geographic locations, since sleep-wake preferences can vary based on distance to the equator.)
In both groups of participants, people who had a later chronotype—those who preferred to stay up late and do activities in the evening—reported more depression symptoms than those with early chronotypes. This was true even after the researchers adjusted for sleep quality, age, gender, and other factors that could affect depression rates.
The findings are important because depression is common in patients with diabetes, says lead investigator Sirimon Reutrakul, MD, associate professor at Mahidol University Faculty of Medicine in Thailand. What’s more, untreated depression can make it harder for people to manage their diabetes, she adds, and can contribute to poor self-care, poor blood glucose control, and diabetes complications.
The study was not able to prove a cause-and-effect relationship in either direction, and Dr. Reutrakul says the association between depression and chronotype was “only modest.” But she says the findings do support a link between circadian regulation and psychological functioning in people with diabetes.
Learning more about this relationship might help doctors develop strategies to improve mental and physical health in patients with diabetes, Dr. Reutrakul adds. For example, future studies could investigate whether treatments for circadian imbalances—like light therapy and melatonin—might also be helpful for managing depression symptoms.
But for people with diabetes who are natural night owls, Dr. Reutrakul says it’s unclear whether forcing a change in sleep patterns is a good idea. “I think everyone has their own timing, and it remains to be seen whether going to bed earlier and waking up earlier would help,” she says.
For now, she adds, it’s helpful for people with diabetes to simply be aware of the association, and to know that a later chronotype is another risk factor for depression.
The study also found that poor sleep quality was also associated with more depression symptoms, which is something that both early birds and night owls can work to improve. “Getting adequate, regular sleep, and being consistent in terms of sleep timing, is a good idea no matter what,” she says.