About Your Mood  Mood Research

Depressed Mood Can Weaken Immune System

Even a mild case of the blues can suppress your immune system and make you more likely to get sick, and it gets worse if you're older and have been "blue" for a long time. New research from Ohio State University, published in the current issue of the Journal of Abnormal Psychology, found older adults who had symptoms of depression also had decreased immune system function.

"Even a mild level of depressive symptoms can have important implications for older adults and their health outcomes," said lead researcher Lynanne McGuire, who is now a post-doctoral fellow in the Behavioral Medicine Clinic at Johns Hopkins School of Medicine in Baltimore.

About 2 million Americans over the age of 65 are believed to have diagnosable depression, according to the National Institute of Mental Health. However, the new study says another 12 percent to 20 percent in this age group could have milder cases of mood disorders.

McGuire and her Ohio State colleagues examined 78 adults whose average age was 72.5 years. Just over half of them were caring for spouses with dementia. The group completed psychological evaluations, and had blood tests at the start of the study and again 18 months later. From the psychological evaluations, the researchers found 22 people had symptoms of depression - 15 from the caregiving group and seven from the non-caregiver group.

Then, they tested the blood to look at one part of immune function - T-cell production. T-cells are "killer" cells in the immune system that attack foreign cells, such as those found in viruses and some types of cancer.

"On average, people with depressive symptoms showed poorer T-cell responses," McGuire said, which means depressed patients would be more susceptible to infectious diseases and probably some cancers. The study suggests there is a biological process that accompanies depression. However, she added, researchers can't yet explain why such changes take place.

People often don't like to complain about feeling blue, and don't tell their physicians how they're feeling. Therefore, it's important for older adults to remain active and social. If you're feeling down, join an activities center in your area or take a class - anything to get out of the house and around other people.

Source: USA Today