Depression is on the rise, affecting an additional 20 percent of people in United States every year. The mental illness has been associated with a slew of health issues like weight gain, heart disease, and increased risk for infections—and according to a new study published in The Journal of the American Medical Association, might even be causing more medical mistakes.

A team of international researchers scoured studies and surveys conducted over the past 52 years and found that doctors are at high risk for depression. Their symptoms—which include fatigue, inability to focus, diminished motivation and mood, and even suicidal thoughts—could pose higher risks for patients.

Analyzing the results of 54 studies, which included more than 17,500 physicians, the researchers found that close to 30 percent of those entering residency showed symptoms of depression, and the number is growing.

“We also found evidence of a small but significant increase in depression over time, with higher levels of depression among recent residents compared to those who trained decades ago,” senior author Srijan Sen, an Associate Professor of Psychiatry at University of Michigan, says in an interview with Research Gate. He explains that the team decided to look into the statistics after enduring high levels of stress themselves and observing colleagues struggle under the strains of residency training. While the study doesn’t shed light on the specifics behind the increase of depression symptoms in doctors, Sen believes emotional and physical strain are likely caused by long hours and lack of sleep. He also highlights that the symptoms can lead to a dangerous stress cycle, resulting in more medical mistakes made.

“Depression strongly affects work functioning,” he says. “The evidence suggests that doctors who are depressed are substantially more likely to commit medical errors. In turn, medical errors increase the risk of depression in doctors.”

Because solutions were outside the scope of the study, the researchers called for more research into strategies that might help doctors mitigate the stress that leads to depressive symptoms and stop the situation from getting worse.

“At a minimum, we should provide residents and training directors with evidence-based tools that have been shown to be effective in preventing the onset of depression and better access to treatment after depression has developed,” Sen says. “To make a more dramatic impact on depression, more systematic changes in the medical education system may be necessary.”