Chronic Pain Intensity and Psychological Distress Have Differing Effects on Outcomes

Although both chronic pain and depression and/or anxiety negatively impact daily living, a study published in Frontiers in Pain Research found little correlation between the effects of the 2 processes on outcomes.

Researchers sourced data from the Swedish Quality Registry for Pain rehabilitation (SQRP), in which adults (N=40,184) living in Sweden with chronic, nonmalignant pain, were registered in the SQRP between 2008 and 2016. Patient-reported outcome measures (PROMs) were related with pain intensity, psychological distress, interference, lack of life control, and social support using a partial least-squares structural equation modeling approach.

The study population comprised 27.9% men, they had a mean [SD] age of 43.2[11.4] years, Multidimensional Pain Inventory (MPI) pain severity score was 4.3[1.2] points, 36-item Short Form (SF-36) physical function score was 48.7[23.2] points, 38.0% had anxiety, and 33.0% had depression. Overall, 20,986 were grouped as having low distress and 19,288 as having high distress. All variables, except sex, differed significantly between the distress groups (all P <.001).

In 2 direct effects models that evaluated the path of psychological distress and pain intensity, pain intensity had a strong association with interference (f², 0.454) and weak effect on lack of life control (f², 0.156), whereas psychological distress had a stronger association on lack of life control (f², 0.547) than on interference (f², 0.262).

In both models, all mediating effects were significant. For example, pain intensity mediated the relationship between psychological distress and interference (effect, 0.18) and between psychological distress and lack of life control (effect, 0.06) in model 1 (psychological distress affects pain intensity). In model 2 (pain intensity affects psychological distress), psychosocial distress mediated the relationship between pain intensity and interference (effect, 0.11) and between pain intensity and lack of life control (effect, 0.22).

When the same 2 models were tested among the subgroups with low and high distress independently, the direct effects between pain intensity and psychological distress were significantly stronger in the high-distress group (f2, 0.38 vs 0.22), and the direct effects between psychological distress and intensity were weaker in the high-distress group (f2, 0.17 vs 0.20) compared with the low-distress cohort, respectively.

These models best explained the variance in interference (R2, 0.426), followed by lack of life control (R2, 0.349), and psychological distress (R2, 0.047) for the low-distress group and lack of life control (R2, 0.378), interference (R2, 0.359), and psychological distress (R2, 0.142) for the high-distress group.

These findings may not be generalizable for a more diverse and less sex-skewed patient population.

Study authors concluded, “[I]t seems that anxiety and depression impair function and the ability to lead socially meaningful lives to a greater extent, whereas higher pain levels have a more detrimental effect on physical functioning in chronic pain states. The relative strengths of pain intensity and psychological distress on the two impact constructs depend on the underlying assumption concerning the pain intensity-psychological distress relationship.”

This article originally appeared on Clinical Pain Advisor