What is the relationship between anxiety and depression and chronic pain?
A cause and effect relationship between chronic pain and depression and anxiety may be present. However, the exact relationship has yet to be defined and continues to be a topic of debate among clinicians and researchers. One 4-year longitudinal study in the Netherlands found that there appears to be a synchrony of change in anxiety, depression, and pain over time. However, even after their anxiety and depression are in remission, subjects reported higher pain ratings. It was concluded that even a history of depression and anxiety puts individuals at higher risk for chronic pain.
There seems to be an association between chronic pain and depression in different ethnic groups. However, reporting varies across ethnic groups and there are differences in health seeking behavior across groups, and this makes gathering data difficult. There are also differences due to cultural barriers regarding expression of concern about mood and pain, coping strategies, and language barriers. These aspects need to be taken into account and addressed when managing chronic pain and depression in minorities.
It has been found that the association between obesity and back pain is stronger in people who have an emotional disorder. This association is still present after accounting for the prevalence of emotional disorders in those who are obese. Obesity, depression, and anxiety are all recognized as inflammatory states and higher levels of proinflammatory cytokines that have been shown to have a relationship with the progression to chronic pain. Therefore, one hypothesis regarding this relationship is that people with an emotional disorder may be sensitized to experience pain, and this may be magnified by the presence of the inflammatory state associated with increased adipose tissue. This suggests that weight loss counseling may be especially important for those patients who are obese and have comorbid depression and/or anxiety.
Depression and anxiety are more common in patients with chronic headaches than episodic headaches, and have a significant impact on quality of life in patients with both episodic headaches and chronic headaches. Depression and anxiety have a significant impact on employment status, earnings, career success, and these patients feel less understood in general, according to one Austrian study. Persisting anxiety in the early phase of acute neck pain and depression at baseline have been found to be risk factors for poor self-reported recovery and may contribute to the transition from acute to chronic neck pain. Therefore, these factors should be addressed early in the course of the illness.
A more recent theory regarding the relationship between mood disorders and chronic pain is that emotions lie at the interface between physical and psychological processes. Therefore, it has been hypothesized that emotional processing deficits play a role in the development of chronic low back pain (CLBP). The results of one study exploring whether patients with chronic low back pain process their emotions differently compared to asymptomatic individuals suggests that dysfunctional emotional processing is indeed associated with chronic low back pain. However, a causal relationship has yet to be established. One hypothesized model is the fear-anxiety-avoidance model, which proposes that pain-related anxiety and anxiety sensitivity are important factors in the development and maintenance of chronic musculoskeletal pain.
Attempts have been made to identify syndromes that might unify the presence of multiple comorbidities, including anxiety, mood disorders, and chronic pain. For example, one such proposed syndrome is called anxiety-laxity-pain-immune-mood (ALPIM) syndrome. A study found significant relationships between a cluster of comorbidities that includes a core anxiety disorder, joint laxity, chronic pain syndromes, immune disorders, and mood disorders. It is therefore postulated that there may be a genetic predisposition for development of ALPIM.
Researchers have attempted to elucidate the biological basis of the relationship between chronic pain and psychological disorders. One study using a rat model of neuropathic pain shows that chronic neuropathic pain leads to affective behavioral dysfunctions related to classical anxiety and depression symptoms. These changes are accompanied by a noradrenergic impairment similar to that described for depressive disorders. A theory regarding the neurobiological basis of anxiety and chronic pain proposes that anxiety is mediated through presynaptic long-term potentiation in the anterior cingulate cortex, which is a key region for pain perception, and that postsynaptic long-term potentiation plays a role in the behavioral sensitization to chronic pain.