Men who take hormone therapy for prostate cancer may have a higher risk of depression than patients who receive different treatment for these malignancies, a U.S. study suggests.

Prostate cancer cells need testosterone to grow and spread. Researchers focused on a common treatment known as androgen deprivation therapy (ADT), which works by depriving tumor cells of testosterone. Side effects can include sexual dysfunction, weight gain and fatigue.

Patients with prostate cancer who received hormone therapy were 23 percent more likely to develop depression and 29 percent more likely to have inpatient psychiatric treatment than men who received alternative treatments, the study found.

"The take-home message is that the list of potential side effects of hormone therapy is continuing to grow," said senior study author Dr. Paul Nguyen of Brigham and Women's Hospital and Harvard Medical School in Boston.

"Any man with prostate cancer considering hormone therapy should find out from their doctor exactly how big the benefit is expected to be in their specific situation so they can weigh it against the list of possible side effects," Nguyen added by email.

To explore the link between hormone therapy and depression, Nguyen and colleagues examined data on more than 78,000 men age 66 and older who were treated for prostate cancer from 1992 to 2006.

They followed men for three years, and excluded patients with psychiatric diagnoses in the year before they were diagnosed with tumors.

Almost 45,000 men in the study received hormone therapy, and they tended to have more advanced disease. They were about 76 years old on average, about two years older than the typical age of the men who received different treatments.

From six months to three years after diagnosis, 7.1 percent of the men on hormone therapy had new cases of depression, compared with 5.2 percent of the others in the study.

During this period, 2.8 percent of men on hormone therapy had inpatient psychiatric treatment, compared with 1.9 percent of their peers. In addition, 3.4 percent received outpatient psychiatric services, versus 2.5 percent of the other men.

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One limitation of the study is that researchers didn't have data on drug treatments for depression, the authors note in the Journal of Clinical Oncology. It's also possible that the older age or more advanced tumors of the men receiving hormone therapy might have influenced their odds of depression.

Side effects of hormone therapy such as fatigue, lower libido and sexual performance, and decreased muscle mass may also play a role, said Dr. Sumanta Pal of the City of Hope Comprehensive Cancer Center in Duarte, California.

"Although it's within reason to construe that hormone therapy may have a direct impact on the centers in the brain that control mood, it's important to acknowledge that the side effects of hormone therapy may also contribute to the development of depression," Pal, who wasn't involved in the study, said by email.

Because the risk of depression rose with longer treatment, men who consider hormone therapy may want consider the duration of therapy when deciding whether the benefits are worth the potential side effects, Pal added.

"Prostate cancers that carry a higher risk can either be managed with surgery alone or a combination of radiation with hormone therapy," Pal said. "In the latter scenario, patients with high-risk localized prostate cancer may get up to three years of hormone therapy, apparently putting them at substantial risk for depression."