Genetic factors help to explain the commonly found association between low back pain and depression, according to a large study of twins published in the journal Pain.
Genetic factors affecting both conditions may be involved in the association between back pain and depression.
For the study, Marina B. Pinheiro, MD, University of Sydney, Sydney, Australia, and colleagues analysed 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 analysed 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 times higher for those with symptoms of depression and anxiety.
On analysis of twin pairs, 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 twins.
On further analysis of monozygotic twins 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.
“It still remains unclear whether common genetic factors predispose people to develop both low back pain and depression,” the authors wrote.
They noted that future studies in which participants are followed up over time (preferably twins) are needed to confirm the findings.