Just as I was thinking I understood the full range of depression’s impact on my life, I started finding out about links between the mood disorder and some nasty physical problems. I mentioned in this post the prevalence of pain among depressed people seeking treatment from their regular doctors. But depression can do a lot more to your body than inflict pain. It has been linked to coronary heart disease, congestive heart failure, diabetes and loss of bone mineral density.
The link between the mood disorder and physical impacts, however, isn’t a simple matter of cause and effect. Some physical problems, like chronic pain, may be symptomatic of depression, although it’s not yet listed among the formal diagnostic criteria for a major depressive episode. When depression appears along with cardiovascular disease, congestive heart failure or diabetes, on the other hand, the relationship is not that of symptom to illness. Instead, depression coexists, or in medical terms is comorbid, with independent diseases. It can be a risk factor for the future onset of those conditions, and depression may have the same neurochemistry that causes them.
Here are a few of the facts and theories emerging from recent studies.
The most common physical complaints that depressed people bring to their primary care physicians are pain, gastrointestinal problems and sleep disorders. The leader of the pack is pain.
It comes in many varieties that relate to depression. Chronic back pain, joint pain, arm and leg pain, especially when they seem to have no explanation, are high on the list. In fact, the presence of pain and other physical symptoms that seem to have no cause makes it all the more likely that there is an underlying mood disorder, most often depression.
Why does pain, in particular, so frequently appear with depression? Neuroscience researchers have looked closely at the link. Apparently, there’s an overlap between pathways in the nervous system that help bring on both pain and depression. The neurotransmitters, serotonin and norepinephrine, familiar as the targets of antidepressant medication, also contribute to pain. The evidence seems to say that reduced levels of these hormones can result in both pain and depression.
Unfortunately, treatment usually doesn’t deal directly with pain. However, research is finding that if those problems stay with you after you feel better and seem to be out of a bad episode, you have a greater risk of relapsing. That makes me wonder if I’ve recovered as fully as I thought, since I have my own checklist of chronic physical problems.
Coronary Heart Disease:
Because heart disease is such a widespread killer, researchers have put together a lot of data about the difference that depression makes to heart patients. The findings aren’t good. If you’re depressed and have coronary artery disease, you’re twice as likely as those who are not depressed to have a major cardiac event within 12 months of the diagnosis. You are also a lot more likely to die after a heart attack or coronary bypass surgery. While a number of studies confirm those grim connections, it’s less clear why depression has these effects.
One theory points to impacts on the autonomic nervous system. This is the system regulating vital functions that occur without your awareness, especially the beating of your heart. One part of autonomic system is the sympathetic nervous system. Its function is to stimulate the heart, while the parasympathetic nervous system relaxes it. Depression may increase the stimulation and reduce the relaxation of the heart muscle, and that can lead to a number of cardiac events.
The neurotransmitters linked to depression could affect the arteries as well. When their levels in the blood drop, that reduction may contribute to the chronic inflammatory process that defines coronary artery disease.
Loss of Bone Mineral Density:
All studies haven’t reached the same conclusions, but the majority of them have found connections between depression and decreases in bone mineral density. That leads to osteoporosis and an increased risk of fracture in older adults.
Depression is linked to elevated levels of the steroid cortisol. Too much cortisol may also affect bone metabolism and so reduce mineral density. Estrogen and testosterone production are important for bone health, and depression tends to lower the levels of these hormones as well. A third mechanism by which depression can lead to bone loss is the increased activity of the sympathetic nervous system that affects heart disease.
The behavior of depressed people can also play a role. Depression is associated with less physical activity, and without exercise the body loses an important way of increasing bone mineral density. Smoking and alcohol use are both linked to depression, and both can reduce bone formation.
About 23 million people in the US have diabetes, and a ten year study, lasting from 1996 to 2006, has found a link with depression. The study tracked more than 65,000 women between 50 and 75 years old. Those who were taking antidepressants were 25% more likely to develop diabetes than women who were not depressed. Women with diabetes were almost 30% more likely to get a depressive disorder than women without diabetes. If they were taking insulin, the risk of depression was more than 50% higher.
There are two ways of explaining this connection. One is biological and has to do with the effects of stress. Depression tends to put people into long-lasting stress, and that results in higher levels of cortisol in the blood. That’s the steroid produced by the body to help it deal with threats and high stress situations – which can be psychological as well as external. High levels of cortisol cause numerous problems, and diabetes may be one of them.
The other explanation focuses on the behavior of people with both conditions. Diabetics rely on self-care, including regular insulin injections, and depressed people often fail to take care of themselves. Diabetes can also worsen depression because it is a chronic illness that increases the level of stress and worry in daily life. Since these are also characteristics of depression, they become even worse with the added complication of diabetes.
I first read about the possible effects of depression on these widespread diseases in Peter Kramer’s Against Depression. He argued that such physical effects made it all the more urgent to begin depression treatment as early as possible. Successful treatment of depression at its first appearance increases the chances of preventing the illness from becoming recurrent. And it is the continuing distortion of the body’s neurochemistry caused by repeated episodes depression that greatly increases the risk of developing other serious diseases later in life. That’s a strong motive for finding effective treatment as soon as possible.