Aug. 29, 2002 -- Across cultures, patients who complain of pain tend to be depressed. The finding comes from a huge international study by Prozac manufacturer Eli Lilly and Company.
Eli Lilly is a WebMD partner.
"Chemicals that are related to depression and painful physical symptoms share the same pathway along the nervous system [the body's nerves and brain]," Robinson says. "An imbalance in these chemicals may explain the frequent presence of painful physical symptoms in depressed patients. That is, the imbalanced chemicals may be sending more intense messages that there is too much pain. It's not that the pain is 'in your head' as once believed. When you have depression there is a chemical reason why you may truly feel more pain."
Patients often feel less pain when their depression gets better, says Charles L. Raison, MD, assistant professor in the mind/body program at Atlanta's Emory University.
"It is a two-way relationship," Raison tells WebMD. "Not only does pain cause depression, but if people get depressed they will experience more pain. We do testing where you have this little wand that gets uncomfortably hot. When people are depressed, they will complain that touching the wand hurts. When you get them undepressed, the same temperature doesn't hurt them."
Robinson's study looked at 18,456 patients seen by primary-care doctors. The patients were from all over the world: Spain, Israel, Brazil, Australia, Russia, and the U.S. They took brief tests for depression and severity of pain.
No matter where they came from, Robinson found the same thing. Patients who came in complaining of pain tended to be depressed. Overall, patients with pain were nearly three times more likely than other patients to report high levels of depressive symptoms.
"Depressed patients often present with emotional and physical symptoms: general body aches and pains, headache, abdominal pain/GI disturbances, and joint pain," Robinson says. "Painful complaints can be part of the depression and not necessarily a different, simultaneous condition. Pain is a symptom that may not have a clear source or may cut across many conditions at the same time."
Michael R. Von Korff, ScD, associate director of the Center for Health Studies at Seattle's Group Health Cooperative, has studied the relationship between pain and depression.
"There is evidence from people with both pain and depression that if the pain resolves, their depression gets better," Von Korff tells WebMD. "If their pain is chronic, their depression is more likely to stay elevated. There is also lots of evidence that people who have multiple pain problems tend to have high rates of psychological illness -- depression in particular. Are people prone to depression more likely to develop pain problems? If people who have no pain get depressed, are they more likely to develop new pain problems? There are studies supporting both sides of the issue."
There is strong evidence that antidepressant drugs relieve pain, Raison says. It takes several weeks for these drugs to have an effect on depression. It takes just as long for them to work on pain. This suggests that they act on a brain system that underlies both depression and pain.