“…There is also some concern regarding the construct validity of the WCQ because the existing evidence is based primarily on exploratory factor analyses [7]. In recent years, there has been a growing use of the WCQ in clinical settings involving cancer [8,9], multiple sclerosis [10], Parkinson's disease [11], fibromyalgia [12], stroke [13,14], chronic fatigue syndrome [15], and spinal cord injury [16]. As was the case for the studies on healthy subjects, studies performed on patients have not confirmed the construct validity of the WCQ, nor are they in agreement regarding alternative factor structures [8,15,17 -19].…”