Low vitamin D has been hailed as critical to bone and muscle development, and suspected as a factor in certain diseases, now including depression. A new study from Oregon State University (OSU) found that healthy young women with vitamin D deficiency have higher incidence of clinical depression, a disabling mental disorder that cloaks a person with profound sadness, feelings of unworthiness, anxiety, hopelessness and sometimes thoughts of death. The study was published in March 2015 in the journal Psychiatry Research. While the findings didn’t make a causal link, the research suggests there’s at least a “relationship” between depression and low levels of vitamin D, according to the study’s lead author, David Kerr, PhD, an associate professor at OSU’s School of Psychological Science. “Depression has multiple powerful causes, and if vitamin D is part of the picture, it’s just a small part,” Dr. Kerr says in OSU’s news release. “But given how many people are affected by depression, any little inroad we can find could have an important impact on public health.”
The Scope of Depression
According to the World Health Organization, some 350 million people globally suffer from the serious illness, also known as major depressive disorder. In the U.S. alone, an estimated 25.2 million Americans — about 7 to 8 percent of the U.S. population — are suffering from depression. According to Richard Shelton, MD, a professor and the vice chair of research at the University of Alabama, Birmingham’s Department of Psychiatry and Behavioral Neurobiology, one-third to one-half of people with depression don’t respond to existing treatment, which includes antidepressant medications, psychotherapy or both. And depression isn’t just the leading mental illness, but a leading cause of suicide as well. According to the latest data reported by the Centers for Disease Control and Prevention, depression claimed the lives of 40,600 people in the U.S. in 2012. Dr. Shelton, who’s conducted clinical trials for new depression medications, says there’s obviously an urgent need to understand depression better and to help those with the disease. That’s what the OSU team sought to learn with its study. Prior research has actually found no tie between depression and vitamin D, but that research focused on older women or those with specific medical conditions, Kerr said.
How Do You Get Vitamin D?
Vitamin D is produced in the body by being out in the sunlight, but during the winter and in locations where natural sunlight is limited or harder to get, vitamin D can be found in foods such eggs, cheese, fatty fish like tuna, mackerel and salmon, and foods fortified with vitamin D like milk, cereal and orange juice. There are also vitamin D supplements with a recommended daily allowance of 600 IU per day. Vitamin D is vital to bone and muscle function, and lack of it has been linked to various conditions, such as decreased immunity and some forms of cancer, says the study’s co-author Adrian Gombart, PhD, an associate professor of biochemistry and biophysics, principal investigator of OSU’s Linus Pauling Institute, and an international expert on vitamin D and the immune response, in the news release.
Depression, Vitamin D and the Weather
Young women in the Pacific Northwest were the focus and subjects of the OSU study because more rain and less sun put them at higher risk for vitamin D deficiency and depression. The researcher chose women because statistics show that 25 percent of women in the U.S. have had depression during their lifetimes, whereas 16 percent of men experienced it in their lives. Over the course of a school year, the students’ vitamin D levels were measured in blood tests, and the women answered surveys about depression symptoms weekly for five weeks. Despite their overall good health, many of the women in the study suffered vitamin D deficiency, and women of color experienced far greater deficiencies at 61 percent versus 35 percent in other women. What’s more, over the course of the study, more than one-third of the study subjects said they had clinically significant depressive symptoms each week. “It may surprise people that so many apparently healthy young women are experiencing these health risks,” Kerr says in the news release. It was no surprise, he added, that vitamin D levels dropped in the fall, bottomed out in winter, and rose in the sunnier months of spring and summer. Research examining vitamin D in women of color is already underway at OSU. What’s next: This study found what appears to be a link between depression and vitamin D, but there’s no causation, so the researchers believe the next step is to conduct a clinical trial with women who are given vitamin D. By Nancy Wride Follow Nancy on Twitter at @NWride