This paper presents a computational agent model that simulates the regulation of sensory processing and behavioural responses to stimuli in autism spectrum disorder (ASD). The model incorporates feedback loops and accounts for the heterogeneity, variability, and adaptivity of these behavioural responses. We specifically investigate how epigenetic mechanisms, or the modulation of gene expression by environmental factors, can influence sensory processing sensitivity, or the responsiveness to subtle sensory signals, in ASD. We evaluate our model with simulation experiments.