“…Studies include between 20 [19] and 1531 [15] patients and are conducted in Australia [19,28], Denmark [14,34], France [31], GB [17,22], Germany [21,23,27,29,32,33], Italy [24], Netherlands [35], Norway [18], Switzerland [30], and the USA [15,16,20,25,26]. Five studies focus on patients with chronic pain [21,23,30,32,33], four studies on patients undergoing palliative care [16,19,20,26], and two studies on patients with neurological diseases (Parkinson's disease (PD) [24], multiple sclerosis [14]), cancer [27,31], or severe mental illness [34,35].…”