Treating depression may have an added benefit for people with diabetes — longer life.
A large new study from Taiwan found that antidepressants cut the risk of dying during the study period by more than one-third for people with diabetes and depression.
"The first nationwide population-based study showed antidepressant use was associated with significantly reduced mortality by 35% among patients with diabetes mellitus and depression," said study senior author Dr. Vincent Chin-Hung Chen, a professor in the School of Medicine at Chang Gung University in Taiwan.
Chen said that while the study didn't look for what the underlying reason for the benefit might be, past research suggests several reasons why antidepressants might lower the risk of dying for people with diabetes and depression.
First, antidepressants may lower someone's risk of suicide. These medications also improve mood, which may lead to better diabetes management.
The drugs also have biological effects that may reduce the risk of other conditions, such as heart disease, according to Chen. Antidepressants reduce inflammation in the body, and they help keep the blood thinner, which may help prevent blood clots.
People with diabetes are two to three times more likely to experience depression, according to the U.S. Centers for Disease Control and Prevention. Many of those people will go untreated. The CDC estimates that between 50% and 75% of people with diabetes don't get treatment for their depression.
The new study looked at more than 53,000 people in Taiwan who had newly diagnosed diabetes who were also diagnosed with depression. Chen said the study included people with both type 1 and type 2 diabetes.
The study was conducted from 2000 to 2013. Chen said the average follow-up period was just over seven years for those who died, and 10 years for those who didn't.
A large majority of people in the study — just over 50,000 — used antidepressants. Only about 3,000 people did not.
The researchers attempted to control the data to account for things that might affect the risk of death. Some examples of things they controlled for included other illnesses, age, sex, income, where people lived and the severity of diabetes.
The researchers said the reduced risk of death was seen in different classes of antidepressants.
Chen noted that the study can only show an association between antidepressant use and a lower risk of death. It cannot prove cause and effect.
One type of antidepressant — called a reversible inhibitor of monoamine oxidase A (RIMA) — was associated with an almost 50% higher risk of death. In Taiwan, only one drug in this class (moclobemide) is approved. This drug isn't approved for use in the United States.
Chen said it's not clear why people taking this drug had a higher risk of death. However, he said the drug is typically prescribed to people who have more serious depression, and who have not responded to other medications.
Amanda Spray, a clinical assistant professor in the department of psychiatry at NYU Langone Health in New York City, said the findings made sense.
"Depression can interfere with someone's ability to take care of themselves and adhere to medications as prescribed, as well as to make healthy lifestyle changes like exercise and a healthy diet," she said.
Spray said while it's not clear from the study if the benefit stems from improved depression or biological changes caused by the medications or a combination of factors, she suspects that psychotherapy might also provide a similar benefit. She added that it would be great to see a study comparing antidepressants and therapy in people with diabetes and depression.
"For me, the biggest takeaway from this study is that this is just another example of how intertwined mental and physical health are," Spray said.
Study author Chen said the study highlights the need for people with diabetes to be screened and treated for depression.
The study was published July 2 in the Journal of Clinical Endocrinology and Metabolism.