170 Chapter 8 An important conclusion of both Ammerman e.a. (2018) (36) and Liu (2017) (41) is that, based on most behavioral and imaging studies, NSSI is considered a conditioned, reinforcing behavioral act, aimed at emotion regulation, which results in a habitual rewarding experience. The reward system might therefore be of great interest when further investigating the neurobiological etiology of NSSI. RESULTS: PSYCHOPATHOLOGICAL AND NEUROBIOLOGICAL OVERLAP BETWEEN AN AND NSSI AN and NSSI: psychopathological overlap As mentioned above, there is a high rate of co-occurrence between EDs and NSSI. Cucchi et al (2016) (49) found a lifetime prevalence of NSSI in 22% of the AN patients and in 33% of the bulimia nervosa (BN) patients. This seems logical because both NSSI and purging require proactive deliberate action, whereas restricting is a more passive action (50). Claes & Muehlenkamp (2014) (51) define both NSSI and ED related behavior as ‘harmful behaviors falling within a behavioral spectrum ranging from self-care to self-harm’. The behavioral symptoms of EDs and more specifically of both subtypes of AN (AN-R and AN-BP) do have a highly (self-) destructive character. Because of the level of self-destructiveness in AN (and other EDs), and the assumed function of eating disorder symptoms in emotion regulation, some authors even suggest to consider EDs itself as a form of non-suicidal self-injurious behavior (NSSI) (13). The onset of both AN and NSSI is usually during adolescence, and both show a trend towards a higher prevalence in the female population. Both NSSI and EDs share important risk factors like experienced childhood trauma, especially sexual abuse, or other traumatic events. Claes & Muehlenkamp present a conceptual model based on the psychosocial risk factors that are shared by NSSI and EDs (figure 1, derived from Claes & Muehlenkamp (2014) (51). In addition, Svirko and Hawton (2007) (13) systematically reviewed the literature on psychological associations between NSSI and EDs. The most important shared psychological factors besides affect/emotion dysregulation implicated in EDs and NSSI are impulsivity, obsessive-compulsivity, dissociation, self-criticism/self-punishment and a need for control. Furthermore, associations are found with perfectionism, body-dissatisfaction and identity-conservation (52). Both NSSI and EDs are considered to be related to emotion dysregulation (49, 53-55). The behaviors function as maladaptive coping strategies that can be seen as a form of self-destructive behavior, to either escape or generate specific feelings. NSSI as well as eating-disordered behavior are
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