In the U.S., nearly 100 million people suffer from chronic pain. Regardless of how it begins, chronic pain is defined as pain that is refractory, lasting longer than three months. There are many side effects of chronic pain, but one that seems to exponentially worsen symptoms is depression. Researchers have long studied chronic pain’s relationship to depression, but recent research has looked to see if depression can actually cause chronic pain. The answer? Chronic pain and depression have a strong connection, with one increasing the chances of the other.
Chronic pain and depression: How chronic pain occurs
It is important to understand that chronic pain is more than pain that continues after an injury or accident. Michael Clark, psychiatrist and director of the pain treatment program at Johns Hopkins Hospital, noted that chronic pain actually changes the structure of the brain:
“[Chronic pain] has greater intensity, causes impaired function and can migrate beyond the original pain site. The nervous system becomes distorted. Pain receptors get amplified and internal pain blockers minimized, which can make even the lightest touch be perceived as painful.”
This intensity of pain that has changed the brain can be difficult for friends and family members to understand. Because of that, chronic pain is an isolating condition. The “invisible” nature of the illness may leave others skeptical, and that doubt among loved ones can be wearing.
In addition, chronic pain and its attendant medications can cause other side effects such as sleep disorders, cloudy thinking, and general malaise (a feeling of being unwell). Chronic pain patients may experience changes in appetite, nausea, and digestive upset.
How chronic pain can lead to depression
All of these side effects create the perfect environment for depression to settle in and take hold. One study found that the incidence of major depression among patients with low back pain was three to four times the rate in the general, healthy population. Another study found that as the severity of the pain rose, the prevalence of major depression rose at the same rate.
The side effects of chronic pain seem to contribute to the severity of depression. Lack of sleep due to pain or as a side effect of medication can increase pain sensitivity during the day, which can also increase pain at night. Sleepless chronic pain patients may find themselves snapping at their families during the day, adding stress to the home environment.
The impact of this family conflict can also be more pain and depression. One study of workers who missed more than 28 days of work due to pain found that their inability to contribute to the family in their usual way (e.g. through work, household chores, or other family responsibilities) led to depression and anger. This could then lead to feelings of isolation, which are not helpful for chronic pain and depression, either together or separately.
Salim Hayek, MD, a cardiology research fellow with Emory Clinical Cardiovascular Research Institute, found that the road to depression from chronic pain is actually a well-established two-way street. Not only does chronic pain cause depression, but depression also seems to cause pain, both chronic and acute. Hayek and his colleagues looked at 5,825 patients enrolled in the biobank (a registry of potential cardiac patients) from 2004 to 2013 at Emory University. Among both men and women, patients with depression were three times more likely to experience chest pain, with or without the presence of coronary artery disease.
Hayek noted the previously established connection between chronic pain and depression, but went on to explain the little-known converse relationship:
“Depression is a common and well-recognized risk factor for the development of heart disease. Patients with known heart disease and depression tend to experience chest pain more frequently. However until now, it was not known whether that association was dependent on underlying coronary artery disease. We found that depression is strongly associated with the frequency of chest pain in adults, with and without underlying coronary artery disease, and that patients with depression and heart disease did not have an improvement in their chest pain frequency even after coronary intervention. One possible explanation for our findings is that pain and depression share a common neurochemical pathway.”
This changed neurobiology makes the brain and the body more susceptible to both chronic pain and depression.
Treating chronic pain and depression
In Hayek’s study, it was interesting to note that even in patients who received successful treatment that resolved their coronary artery disease, the pain remained if the depression was left untreated. Because chronic pain and depression are so closely connected, therapies to treat one may work on the other.
Some treatments for managing both chronic pain and depression can include:
- Antidepressants: Even in patients without depression, antidepressants are often prescribed for chronic pain. How they work in the body is unclear, but it may have something to do with pain and depression sharing the same neural pathways.
- Counseling: Cognitive behavioral therapy or other talk therapies can help patients with chronic pain and depression regain a sense of control over their health.
- Stress management and lifestyle changes: Stress management techniques can include things like using mindfulness meditation, yoga, t’ai chi, or other exercise to help reduce stress that can increase both chronic pain and depression. Lifestyle changes could incorporate dietary changes as well as self-care regimens that can offer physical and mental comfort.
Due to the complex nature of chronic pain and depression, both together and as separate conditions, the best management plans seem to combine a number of different methods that address both physical and mental symptoms.
If you suffer from chronic pain or depression, talk to your doctor about treatments that address both conditions.