Depression is a disorder of the body as much as of the mind. Consider that several of the core symptoms of the condition manifest in body systems: depression invariably expresses itself in a change of appetite, usually inhibiting the desire to eat, but occasionally reversing course, as in atypical depression, and increasing it.
Similarly, the body's need for restorative sleep is profoundly disturbed, and nearly all depressed individuals experience sleep problems; 80% complain of insomnia, another 15% sleep excessively. Insomnia by itself appears to be a risk factor for depression. Most patients complain of body fatigue. In many, energy loss is so overwhelming that physical movement is arduous and grinds to a paralyzing halt.
Increasingly, there's evidence that depression involves various body systems. There seems to be a complex relationship between depression and the heart. Depression raises the risk of heart disease; it also magnifies the deadliness of existing cardiac problems. It's not clear why, although researchers have found that depression alters blood platelets, circulating elements that are responsible for clotting.
What's more, depression leaves footprints on the body's structure as well. For example, it accelerates changes in bone mass leading to osteoporosis.
But of all the signs that depression has a neck-down presence, none is more insistent than physical pain. For a substantial number of people, possibly up to half of depression sufferers, bodily pain is the way depression presents itself.
The pain is often vague and unexplained by injury. It may show up as headache, abdominal pain, or musculoskeletal pains in the lower back, joints and neck—alone or in any combination. The painful physical symptoms of depression typically take the form of multiple somatic complaints.
The trouble is, too often neither sufferer nor doctor is aware of the true source of the problem and the depression goes untreated as well as unrecognized. It's not that the pain is "all in the head." No, the pain is indeed real, but it likely drives many people to primary care physicians or orthopedists in the mistaken belief that something has gone awry in their body. And there follows an unproductive search for an organic source.
"We're becoming more sensitized that major depressive disorder has physical as well as emotional symptoms," says Stephen M. Stahl, M.D., Ph.D., associate professor of psychiatry at the University of California San Diego. He believes that the many unrecognized cases of depression—some estimates put the figure as high as 50% of all cases—may be the ones that do not complain of depressed mood."
Physical symptoms are as important in treating the condition as in recognizing it. "Even where people have emotional symptoms of depression—and many people have both emotional and somatic symptoms—they are not necessarily well when their emotional symptoms improve," says Dr. Stahl.
Failure to eliminate the pain symptoms reduces the chances of full recovery. Persistent pain typically keeps depressed people from regaining full function in the personal and professional lives, and it raises the danger of suicide.
Depression has long been associated with pain. But it was once thought that people with pain were somehow "denying" their emotional disorder and converting it into bodily pain. The new view is that somatic complaints are the way some people get depressed. There is actually something malfunctioning in their pain perception pathways.
In a study of over 25,000 patients at 15 primary care centers on five continents, Seattle researchers found that 50% of all depressed patients worldwide report multiple unexplained physical symptoms. It's wasn't that such patients were any less willing or able to express emotional distress. They readily acknowledged depressed mood when specifically asked about it.
Nor were there differences in the frequency of pain symptoms among Western and non-Western cultures. The researchers concluded that "somatic symptoms are a core component of the depressive syndrome."
Like the emotional symptoms, the painful physical symptoms of depression arise in specific nerve pathways presided over by the neurotransmitters serotonin and norepinephrine. From their base in the brainstem, such pathways travel up into the highest reaches of the brain, the frontal cortex, where they help regulate thinking and mood. They also travel up to the brain's hypothalamus, where they regulate eating, sleeping, and sex drive.
But serotonin and norepinephrine pathways also travel down into the spinal cord serving the rest of the body. And therein lies the problem.
As the body goes about its tasks, explains Dr. Stahl, there are constant sensations associated with the routine functioning of the body, such as digestion in the stomach and abdomen. The central nervous system is also fed routine inputs from the musculoskeletal system throughout the body. But normally those sensations are suppressed from consciousness and ignored. That's what allows you to pay attention to the world outside your body.
And that suppression is normally accomplished by serotonin- and norepineprhine-dependent nerve fibers descending from the brain into the spinal cord. But they become dysfunctional in depression and fail to operate efficiently. As a result, routine sensory input "escapes" up into the brain, where it is interpreted as uncomfortable or even painful physical symptoms when in fact nothing is wrong.
"There are mechanisms for pain to be suppressed," explains Dr. Stahl. "If they're not working right even false discomfort can be perceived and magnified."
All effective antidepressants work on relieving somatic symptoms—to some degree, says Dr. Stahl. But some drugs work more robustly than others. "The emotional symptoms might be improved with agents that boost either dopamine, norepinephrine, or serotonin. But to get the optimal reduction of pain symptoms may actually require an approach that combines action on serotonin and norepinephrine." In other words, the use of dual-action agents.