Chronic pain is a word-wide major health problem, which seriously affects the quality of life of those who experience it and causes important socio-economical costs (Tsang et al., 2008). According to the results of the last Chilean National Health Survey (2010), 34.2% of Chileans older than 15 years present pain ranging from moderate to severe. The pain experienced by a considerable proportion of these individuals (73.5%) is chronic. Among Chileans, chronic pain has been found to be related to more sickness leaves, a five-time increase in the use of primary care services, and the presence of depressive disorders (Miranda et al., 2013). In fact, around 35% patients with chronic pain suffer from depression (Gracely, Ceko, & Bushnell, 2012). In the case of some specific pain disorders such as fibromyalgia, this comorbidity is even greater (life prevalence around 90% for depressive symptomatology and 62-86% for major depressive disorder; Gracely et al., 2012). As a result, some authors posit that fibromyalgia and depression are two manifestations of a single affective spectrum disorder (Gracely et al., 2012). In fact, according to some evidence, both disorders share pathophysiological aspects. For example, pharmacological treatment of both fibromyalgia and depression includes the same dual serotonergic and noradrenergic agonists, namely, amitriptyline and duloxetine (Maletic & Raison, 2009).