A new study has found that older men who get testosterone-suppressing therapy for prostate cancer may be at a very high risk of developing depression.

The study, which examined 78,000 men who had been treated for early stage prostate cancer, found that 7 percent of those who got hormone-suppressing therapy became clinically depressed over the next few years — significantly higher than the typical rate of 5 percent, according to a Brigham and Women’s Hospital statement.

Dr. Paul Nguyen, the senior researcher on the project, said that the team took into account the severity of the cancer, his age, and his education, and the results still held. Also, the longer men were on this therapy, the greater their chances of depression.

Scientists aren’t quite sure why hormone therapy raises the depression risk, but it could be because reduced testerone levels have a direct effect on mood. However, it could be indirect effects, like sexual dysfunction and weight gain caused by the therapy.

Hormone therapy is often used to treat prostate tumors because testosterone typically feeds this cancer’s growth. However, studies like this show that doctors and patients have a lot to discuss before immediately jumping to this kind of treatment.

“We know that patients on hormone therapy often experience decreased sexual function, weight gain and have less energy – many factors that could lead to depression. After taking a deeper look, we discovered a significant association between men being treated with ADT for PCa and depression,” Nguyen said in the statement. “This is a completely under-recognized phenomenon. Around 50,000 men are treated with this therapy each year. It’s important not only for patients to know the potential side effects of the drugs they’re taking, but also for the physicians to be aware of this risk in order to recognize signs of depression in these patients and refer them for appropriate care.”