Narcissistic Personality Disorder (NPD) is a complex psychological condition characterized by emotional dysregulation, impaired empathy, and a heightened need for validation. Although it has previously been explained by early environmental factors such as dysfunctional parenting or neglect, recent discoveries provide a deeper understanding of its biological foundations. This paper presents a computational modeling approach to simulate how environmental adversity and epigenetic modifications, in particular DNA methylation of the SLC6A4 gene, interact in the development of NPD. Using a multi-level adaptive network model grounded in the self-modelling framework of temporal-causal networks, five hierarchical levels of adaptation are implemented, ranging from emotion regulation to gene expression and epigenetic control. There are two simulation scenarios presented: one modeling the onset of NPD symptoms in the absence of therapeutic intervention, and another incorporating a hypothetical epigenetic therapy. The results reveal that, without intervention, maladaptive emotional and molecular states become self-reinforcing over time. In contrast, the introduction of therapy initiates upward modulation through the network hierarchy, resulting in restored emotional regulation and normalized gene expression.