178 Chapter 8 the more central domains and constructs of AN and NSSI, focusing on the underlying basis (and partially common) concepts. In this way the overlapping aspects can be investigated in a basic and dimensional way using genetic, neurobiological, behavioral and developmental data, leading to new (and maybe common) preventive and therapeutic options (figure 3). AN and NSSI: a network analysis approach Another way of researching clinical and neurobiological overlap is the network approach. In the network approach mental disorders are conceptualized as causal systems of mutually interacting symptoms (61). Statistical models provide ways to assess centrality of symptoms (i.e. how connected and clinical relevant a symptom is in a network) and to assess so-called ‘bridge symptoms’, that occur in both disorders. In the network approach NSSI and AN are hypothesized to co-occur due to mutual interactions among (shared) symptoms. Moreover, besides symptoms, other variables like environmental factors, developmental factors, cognitive processes and laboratory and neurobiological measurements can also be included in a network analysis. A network analysis might reveal connections and bridges between variables that seem to overlap, like the symptoms of NSSI and AN itself (the various forms of expression of NSSI as well as food restriction, binging and purging), co-occurring affective symptoms regarding mood and anxiety, but also other variables like childhood trauma, impulsivity, obsessive-compulsiveness, perfectionism, focus on the body, self-criticism, need for control, emotion regulation and reward. Based on this review it is hypothesized that maladaptive coping and emotion regulation together with dysfunctional reward processing are central variables. Although establishing centrality and shared symptoms might be of great value to explain co-morbidity, to predict the course of mental disorders, and to target treatment, the network analysis does not fully explain the direction and causality between connecting variables. It may however shed more light on the overlap between NSSI and AN and the shared etiopathogenetic and neurobiological processes underlying both phenomena. This might guide the phenomenological and research domain discussion elaborated on in the above paragraphs (figure 4).
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