Fig. (1) The association between sleep problems and ICPM efficacy in FM. This figure illustrates a significant negative correlation between sleep problems, as measured with the PSQI (total score), and ICPM efficacy (expressed in %) in FM. More precisely, increased sleep problems were associated with the weakest level of ICPM in this population. ICPM indicates inhibitory conditioned pain modulation; FM, fibromyalgia; PSQI, Pittsburg sleep quality index.