Abstract
BackgroundChronic pain has a strong association with major depressive disorder (MDD), but there is a relative paucity of studies on the association between chronic multisite pain and bipolar disorder (BD). Such studies are required to help elucidate the complex biological and psychological overlap between pain and mood disorders. The aim of this study is to investigate the relationship between chronic multisite pain and mood disorder across the unipolar-bipolar spectrum.MethodsWe conducted a cross-sectional study of 149,611 UK Biobank participants. Self-reported depressive and bipolar features were used to categorise participants into MDD and BD groups and a non-mood disordered comparison group. Multinomial logistic regression was used to establish whether there was an association between extent of chronic pain (independent variable) and mood disorder category (dependent variable), using no pain as the referent category, and adjusting for a wide range of potential sociodemographic, lifestyle and comorbidity confounders.ResultsMultisite pain was significantly more prevalent in participants with BD and MDD, for example, 4–7 pain sites: BD 5.8%, MDD 4.5%, and comparison group 1.8% (p < 0.001). A relationship was observed between extent of chronic pain and risk of BD and persisted after adjusting for confounders (relative to individuals with no chronic pain): 2–3 sites RRR of BD 1.84 (95% CI 1.61, 2.11); 4–7 sites RRR of BD 2.39 (95% CI 1.88, 3.03) and widespread pain RRR of BD 2.37 (95% CI 1.73, 3.23). A similar relationship was observed between chronic pain and MDD: 2–3 sites RRR of MDD 1.59 (95% CI 1.54, 1.65); 4–7 sites RRR of MDD 2.13 (95% CI 1.98, 2.30); widespread pain RRR of MDD 1.86 (95% CI 1.66, 2.08).ConclusionsIndividuals who report chronic pain and multiple sites of pain are more likely to have MDD and are at higher risk of BD. These findings highlight an important aspect of comorbidity in MDD and BD and may have implications for understanding the shared neurobiology of chronic pain and mood disorders.
Highlights
Chronic pain has a strong association with major depressive disorder (MDD), but there is a relative paucity of studies on the association between chronic multisite pain and bipolar disorder (BD)
Classification of mood disorder We have previously reported on the classification and internal validity of probable MDD and BD within UK Biobank, using the self-reported data collected via the baseline touch-screen questionnaire [11]
Given that we have identified that chronic multisite pain is more strongly associated with BD than MDD, and that this association persists after adjusting for several important confounders, including other physical morbidities, which are likely to impact on an individual’s chronic pain and mood symptom reporting, it is possible that there is a significant genetic and neurobiological overlap between severe mood disorders such as BD and vulnerability to chronic pain syndromes
Summary
Chronic pain has a strong association with major depressive disorder (MDD), but there is a relative paucity of studies on the association between chronic multisite pain and bipolar disorder (BD). In the Singapore Mental Health Study, chronic pain was the most prevalent comorbid physical condition among participants with BD, affecting 40.4% of these individuals [8]. These initial findings support the need for a better understanding of the relationships between chronic pain and mood disorder in order to improve the clinical management of these challenging to treat conditions. Further epidemiological understanding will lead to the development of biological hypotheses that might explain why chronic pain and mood disorder (depression and/or bipolar disorder) commonly co-occur
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