Figure 2.

A proposed problem cycle in comorbid pain and sleep problem. Reciprocal relationships between pain, anxiety, and sleep make self-reinforcing problem cycles plausible. An example of the process might depict acute pain, which in individuals with vulnerabilities (eg, genetic or enhanced stress reactivity) evokes heightened anxiety, leading to problems in sleep initiation and continuation. Accumulating anxiety and reduced sleep may lead to more intense and widespread pain, and vice versa. Outside of the core cycle are listed subprocesses of the factors in the cycle (eg, physiological anxiety reactions) and factors with interrelationships to the cycle (eg, RLS). These may serve as treatment targets to interrupt the cycle. Factors in bold appeared in this study to have significant associations with recurring sleep problems. RLS, restless legs syndrome.