A simple wearable device such as a smartwatch could one day help prevent the return of major depression by warning people weeks or even months in advance.
New research from McMaster University shows that changes in sleep and daily activity patterns — detected automatically by a wrist-worn tracker — can signal an increased risk of depression relapse long before a person notices symptoms.
Major depressive disorder is a common mental health condition that affects how people feel, think, and function.
Even after recovery, relapse is frequent, with about 60 percent of patients experiencing another episode within five years.
Doctors currently rely on patients reporting symptoms, which often appear only after the illness has already returned.
The new study, published in JAMA Psychiatry, suggests that wearable technology could provide an earlier warning system.
Researchers followed 93 adults across Canada who had previously recovered from depression.
Participants wore a research-grade activity tracker, similar to a fitness watch, for one to two years. The devices recorded sleep patterns and movement, generating more than 32,000 days of data.
Scientists discovered that subtle disruptions in daily rhythms often appeared before a relapse occurred.
People whose sleep schedules became irregular were nearly twice as likely to experience another depressive episode.
One of the strongest warning signs was a reduced difference between daytime activity and nighttime rest, meaning the body’s internal clock was becoming less stable. Spending more time awake during the night after falling asleep was another predictor of increased risk.
These changes typically developed weeks or months before depression returned, suggesting that wearable devices could detect trouble early enough for preventive action.
Because the technology collects data continuously and without effort from the user, it offers insight between medical appointments, when problems might otherwise go unnoticed.
Researchers say the findings highlight how digital tools could transform mental health care. In the future, a smartwatch could alert someone that their risk of relapse is rising and encourage them to seek support, adjust treatment, or focus on improving sleep habits. Clinicians could also use the information to tailor care to individuals who need it most.
Sleep and activity patterns have long been linked to mental health, but this study demonstrates the practical value of monitoring them automatically. By identifying early warning signs, wearable technology could help reduce the burden of recurring depression and improve long-term outcomes.
Experts caution that more research is needed before such systems become widely available, and privacy considerations will also need to be addressed. However, the results offer hope for a future where managing depression involves not only treating symptoms but preventing them from returning.
For millions of people living with major depression, a small device on the wrist could eventually provide a powerful tool for staying well — quietly tracking the rhythms of daily life and helping keep mental health on course.
