Depression,Pain Intensity,and Interference in Acute Spinal Cord Injury

Background:

The high prevalence of pain and depression in persons with spinal cord injury (SCI) is well known. However the link between pain intensity, interference, and depression, particularly in the acute period of injury, has not received sufficient attention in the literature.

Objective:

To investigate the relationship of depression, pain intensity, and pain interference in individuals undergoing acute inpatient rehabilitation for traumatic SCI.

Methods:

Participants completed a survey that included measures of depression (PHQ-9), pain intensity (“right now”), and pain interference (Brief Pain Inventory: general activity, mood, mobility, relations with others, sleep, and enjoyment of life). Demographic and injury characteristics and information about current use of antidepressants and pre-injury binge drinking also were collected. Hierarchical multiple regression was used to test depression models in 3 steps: (1) age, gender, days since injury, injury level, antidepressant use, and pre-injury binge drinking (controlling variables); (2) pain intensity; and (3) pain interference (each tested separately).

Results:

With one exception, pain interference was the only statistically significant independent variable in each of the final models. Although pain intensity accounted for only 0.2% to 1.2% of the depression variance, pain interference accounted for 13% to 26% of the variance in depression.

Conclusion:

Our results suggest that pain intensity alone is insufficient for understanding the relationship of pain and depression in acute SCI. Instead, the ways in which pain interferes with daily life appear to have a much greater bearing on depression than pain intensity alone in the acute setting.Key words: depression, pain, spinal cord injuriesThe high incidence and prevalence of pain following spinal cord injury (SCI) is well established^1–6 and associated with numerous poor health outcomes and low quality of life (QOL).^1,7,8 Although much of the literature on pain in SCI focuses on pain intensity, there is emerging interest in the role of pain interference or the extent to which pain interferes with daily activities of life.^7,9 With prevalence as high as 77% in SCI, pain interference impacts life activities such as exercise, sleep, work, and household chores.^2,7,10–13 Pain interference also has been associated with disease management self-efficacy in SCI.¹⁴ There is a significant relationship between pain intensity and interference in persons with SCI.⁷ Like pain, the high prevalence of depression after SCI is well-established.^15–17 Depression and pain often co-occur,^18,19 and their overlap ranges from 30% to 60%.¹⁹ Pain is also associated with greater duration of depressed mood.²⁰ Pain and depression share common biological pathways and neurotransmitter mechanisms,¹⁹ and pain has been shown to attenuate the response to depression treatment.^21,22Despite the interest in pain and depression after SCI and implications for the treatment of depression, their co-occurrence has received far less attention in the literature.²³ Greater pain has been associated with higher levels of depression in persons with SCI,^16,24 although this is not a consistent finding.²⁵ Similarly, depression in persons with SCI who also have pain appears to be worse than for persons with non-SCI pain, suggesting that the link between pain and depression may be more intense in the context of SCI.²⁶ In one of the few studies of pain intensity and depression in an acute SCI rehabilitation setting, Cairns et al ²⁷ found a co-occurrence of pain and depression in 22% to 35% of patients. This work also suggested an evolution of the relationship between pain and depression over the course of the inpatient stay, such that they become associated by discharge. Craig et al²⁸ found that pain levels at discharge from acute rehabilitation predicted depression at 2-year follow-up. Pain interference also has been associated with emotional functioning and QOL in persons with SCI^1,7,29,30 and appears to mediate the relationship between ambulation and depression.³¹Studies of pain and depression in person with SCI are often limited methodologically to examine the independent contributions of pain intensity and interference to depression in an acute setting. For example, they include only pain intensity^{16,23,25,28,30}; classify subjects by either pain plus depression²³ or pain versus no pain^8,28,30; use pain intensity and interference as predictor and outcome, respectively¹; collapse pain interference domains into a single score¹; or use only univariate tests (eg, correlations).^7,8,25,30 In addition, the vast majority focus on the chronic period of injury. To fill a gap in knowledge, we examined the independent contributions of pain intensity and pain interference to depression, while accounting for injury and demographic characteristics, antidepressant treatment, and pre-injury binge drinking in a sample of persons with acute SCI. We hypothesized that when accounting for both pain intensity and interference in the model, interference would have an independent and significant relationship with depression, above and beyond pain intensity.