Ruminations have been defined as repetitive and passive thoughts focused on depressive symptomatology and its causes, consequences and implications (Nolen-Hoeksema, 1991). In this literature review, we explore two important theories regarding the understanding of mental ruminations: the response style theory (Nolen-Hoeksema, Wisco, & Lyubomirsky, 2008) and the mode of processing theory (Watkins, 2004 ; 2008 ; 2011). Then, we will determine whether rumination can be considered as a transdiagnostic process involved in social anxiety, posttraumatic stress disorder, obsessive-compulsive disorder, eating disorders and alcohol use. Finally, developments of new interventions focused on ruminations will be described as well as empirical evidence regarding their efficacy.