While medical experts have long known of the correlation between psychological and physical health, mental illness was not considered a major risk factor for cardiovascular disease—until a recent series of research confirmed that depression may serve as one of the most significant causes of heart problems.

Approximately 350 million people suffer from depression globally, according to data from the World Health Organization. According to new research, the risk of fatal heart disease in men due to depression is almost the same as the risk from elevated cholesterol levels, obesity, and smoking.  The findings further pointed to a greater need for heart health screenings among patients with depression, in addition to mental health checks for patients with cardiovascular disease.

The causality is twofold, as patients with pre-existing heart disease conditions are more likely to become depressed due to their poor health and otherwise healthy people diagnosed with depression are likewise significantly more apt to develop heart disease, compared to the general population. Viewed across the population, depression accounts for roughly 15% of cardiovascular deaths—comparable to the other known risk factors.

A professor of medicine at Harvard Medical School, Ahmed Tawakol, has conducted extensive research surrounding the connection between stress and heart health, stating that only over the past few decades “has mounting evidence suggested that stress and depression may be more than simple markers of heart disease; they might be important causes.”

While it remains unclear exactly how depression impacts heart health, it is likely that stress hormones play a critical role. Yet leading a healthy lifestyle—including diet, physical activity, managing stress, being smoke-free—is known to be effective in preventing and treating both depression and heart conditions.