Twin study lends new insights into link between back pain and depression
Genetic factors help to explain the commonly found association between low back pain and depression, suggests a large study of twins in the March issue of PAIN®, the official publication of the International Association for the Study of Pain. The journal is published by Wolters Kluwer.
Genetic factors affecting both conditions may be involved in the association between back pain and depression, according to the report by Marina B. Pinheiro, MSc, and colleagues of The University of Sydney, Australia, and Murcia Twin Registry, Spain.
Twin Data Used to Explore Link between Back Pain and Depression
The researchers analyzed data from an established database (Murcia Twin Registry) of nearly 2,150 Spanish twins. Twin studies provide a unique opportunity to elucidate the association between health conditions, by eliminating the genetic and environmental factors contributing to them.
Questionnaire responses were analyzed to determine whether participants with symptoms of depression had higher prevalence of back pain. A series of statistical analyses were then performed to clarify the contributions of genetic factors and early shared environment to the depression-back pain link.
The results showed a significant association between symptoms of depression and low back pain. On initial analysis considering the participants as individuals, rather than twins - and therefore not accounting for genetic and familial factors - the odds of having back pain were about 1.6 higher for those with symptoms of depression and anxiety.
It is not uncommon for those who suffer from chronic pain to feel stressed and depressed at times. This is no surprise, given the fact that “chronic pain” usually means pain that lasts more than three to six months. Prolonged pain appears to set up a pathway in the nervous system that sends pain signals to the brain, even in the absence of an underlying anatomical problem.
Some chronic pain may be due to a diagnosable anatomical problem, such as degenerative disc disease or spinal stenosis, that can cause continual pain until successfully treated. More often, the chronic pain has no clear anatomical cause, as in failed back surgery syndrome or chronic back pain without an identified pain generator. In such cases, the pain is itself the disease.
For some people, the stress and depression resulting from chronic pain can become consuming, and can even worsen and prolong the pain. Increased pain can, in turn, lead to increased stress and depression, creating a cycle of depression and pain that can be difficult to break.
On analysis of twin pairs - which controls for genetic and familial factors that could influence the relationship between depression and back pain - the relationship remained significant, with a 1.7 increase in odds. The association was even stronger - more than a 2.3 increase in odds of low back pain associated with depression and anxiety - on analysis of dizygotic (non-identical) twins, who share half their genes.
Genetic Factors Are ‘Main Confounder’ of Depression/Back Pain Link
On further analysis of monozygotic twins - who are genetically identical - the association between symptoms of depression and low back pain disappeared. This suggested that the strong association found in non-identical twins resulted from the “confounding” effects of common genetic factors influencing both conditions. For example, genes affecting levels of neurotransmitters such as serotonin and norepinephrine might affect the risk of both conditions.
Previous studies have shown a “consistent relationship” between back pain and depression - a combination that may complicate diagnosis and treatment. However, the nature of the association remains unclear. The new study is the first to examine the relationship between depression and low back pain using twin data to control for genetic and familial factors.
Is there a link between pain and depression? Can depression cause physical pain?
Pain and depression are closely related. Depression can cause pain - and pain can cause depression. Sometimes pain and depression create a vicious cycle in which pain worsens symptoms of depression, and then the resulting depression worsens feelings of pain.
In many people, depression causes unexplained physical symptoms such as back pain or headaches. This kind of pain may be the first or the only sign of depression.
Pain and the problems it causes can wear you down over time, and may begin to affect your mood. Chronic pain causes a number of problems that can lead to depression, such as trouble sleeping and stress. Disabling pain can cause low self-esteem due to work, legal or financial issues. Depression doesn’t just occur with pain resulting from an injury. It’s also common in people who have pain linked to a health condition such as diabetes or migraines.
To get symptoms of pain and depression under control, you may need separate treatment for each condition. However, some treatments may help with both:
Antidepressant medications may relieve both pain and depression because of shared chemical messengers in the brain.
Talk therapy, also called psychological counseling (psychotherapy), can be effective in treating both conditions.
Stress-reduction techniques, physical activity, exercise, meditation, journaling and other strategies also may help.
Pain rehabilitation programs, such as the Pain Rehabilitation Center at Mayo Clinic, typically provide a team approach to treatment, including medical and psychiatric aspects.
Treatment for co-occurring pain and depression may be most effective when it involves a combination of treatments.
If you have pain and depression, get help before your symptoms worsen. You don’t have to be miserable. Getting the right treatment can help you start enjoying life again.
The finding that the association disappears after fully adjusting for genetics and familial confounders in identical twins suggests that “genetics is the main confounder” of the relationship between depression and back pain. Thus the commonly found association between these health conditions is probably not a true relationship, as there are other factors influencing it.
However, “It still remains unclear whether common genetic factors predispose people to develop both low back pain and depression,” Pinheiro and coauthors write. Further studies in which participants are followed up over time - preferably twins - are needed to confirm the findings. The authors also suggest that the link between anxiety and back pain warrants further study.
Click here to read “Genetics and the environment affect the relationship between depression and low back pain: a co-twin control study of Spanish twins.”
Article: “Genetics and the environment affect the relationship between depression and low back pain: a co-twin control study of Spanish twins” (doi:10.1097/01.j.pain.0000460330.56256.25)
PAIN is IASP’s official journal. Published monthly, PAIN presents original research on the nature, mechanisms, and treatment of pain. Available to IASP members as a membership benefit, this peer-reviewed journal provides a forum for the dissemination of multidisciplinary research in the basic and clinical sciences. It is cited in Current Contents and Index Medicus.
About the International Association for the Study of Pain
IASP is the leading professional forum for science, practice, and education in the field of pain. Membership is open to all professionals involved in research, diagnosis, or treatment of pain. IASP has more than 7,000 members in 133 countries, 90 national chapters, and 20 special interest groups (SIGs). IASP brings together scientists, clinicians, healthcare providers, and policymakers to stimulate and support the study of pain and to translate that knowledge into improved pain relief worldwide.
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