Smoking and Pain
Question: Why do smokers experience pain more intensely than nonsmokers?
Answer: Previous studies have clearly shown that, over time, smokers report more pain symptoms and greater pain severity than nonsmokers. Among patients with chronic pain, smokers report greater pain severity than nonsmokers with chronic pain. Similarly, previous studies have shown that smokers have greater levels of depression than nonsmokers. Greater levels of depression among smokers is relevant in that smokers with chronic pain have alternations in pain perception.
Based on these observations, we hypothesized that depression could partly explain differences in pain severity among smokers and nonsmokers with chronic pain. In a study that involved more than 1,200 patients with chronic pain, individuals were categorized by smoking status: current smoker, former smoker, or never smoker. In a linear regression model, status as a current smoker was predictive of greater pain severity. However, after including a measure of depression in the regression model, status as a current smoker was no longer a significant predictor of pain severity. Rather, elevated levels of depression among smokers with chronic pain explained the difference in pain scores based on smoking status.
Why smokers have greater rates and severity of depression is a focus of our ongoing research. The mechanisms responsible for the associations between depression, pain, and smoking are not clear. Functional imaging studies demonstrate that discrete brain regions are responsible for modulating pain in response to negative affect in subjects with and without mood disorders. These imaging studies also suggest that depression and smoking may share common neurobiological pathways. Similar genetic, environmental, and other shared mental health factors may contribute to the risk for developing both conditions. The interactions between smoking, depression, and pain also could be influenced by nicotine withdrawal, which could occur insidiously during time intervals between active periods of smoking.
It also has been suggested that rapid dissipation of the systemic effects of nicotine contributes to pain-related symptoms during periods of relative nicotine deprivation. Nicotine withdrawal has been associated with depressive symptoms, but the potential effects of transient depressive symptoms on measures of clinical pain have not been studied. Depression, in turn, may sustain smoking behavior, and smokers with depression may smoke to elevate mood. In addition, pain may be a motivator to smoke. Although many prior studies have analyzed pairwise associations between depression, pain, and smoking status, few have simultaneously considered the potential interactions among all three.
There are several important clinical implications related to our findings. First, the clinician should be aware that smokers will be at risk for reporting greater levels of pain, which could be due, in part, to elevated levels of depression. Second, patients with chronic pain who smoke should be carefully assessed for depression. Prompt and intensive treatment of depression could, in turn, lead to improvements in pain-related symptoms among smokers with chronic pain.
—W. Michael Hooten, MD
Associate Professor of Anesthesiology
Mayo Clinic College of Medicine