ETD

• arousal
• hyperarousal
• insomnia disorder
• mindfulness

Hyperarousal represents a key element of insomnia disorder. Studies showed a sustained activation of autonomic, endocrine, and cortical systems, involving brain regions such as the amygdala, anterior cingulate cortex, and default mode network. According to Harvey’s model (2002), people with insomnia tend to ruminate about their sleep, leading to safety behaviors, which worsen quality of life and sleep. On the other hand, trait mindfulness, meaning the abilities of self-regulating attention and experiencing the present moment, is associated with a different nervous system activation. Higher levels have been associated with changes in physiological markers (e.g., HRV, cortisol), while mindfulness interventions were demonstrated to improve insomnia and reduce ruminative thinking and perceived stress. This thesis evaluated whether trait mindfulness mediates the relationship between insomnia severity and pre-sleep arousal, testing whether lower mindfulness contributes to enhanced cognitive and somatic hyperarousal in insomnia. In this preliminary cross-sectional study, 29 participants (13 outpatients with insomnia and 16 healthy controls) were evaluated at baseline (T0). Both groups completed the PSAS, ISI, and MAAS. Group differences were examined with non-parametric tests. Mediation analyses were conducted within the insomnia group, using MAAS as mediator of the association between ISI and PSAS cognitive, somatic, and total scores. Patients with insomnia reported higher ISI and PSAS, with significantly higher cognitive arousal, and significantly lower MAAS (Median = 51.0; p < .001, r = –.66). Higher ISI predicted greater PSAS (β cognitive = .71, p < .001; β somatic = .48, p = .009; β total = .66, p < .001) and was strongly negatively related to MAAS (β = –.65, p < .001). Lower MAAS was associated with greater PSAS (β cognitive = –.72; β somatic = –.62; β total = –.74; all ps < .001). Mediation analyses showed significant indirect effects for somatic (β = .35, p = .008) and cognitive PSAS (β = .29, p = .035). Mindfulness acted as full mediator for somatic PSAS and partial for cognitive PSAS. Trait mindfulness is an important psychological mechanism linking insomnia severity to pre-sleep hyperarousal, with a stronger influence on somatic arousal. These preliminary results support integrating mindfulness-based strategies into interventions targeting hyperarousal in insomnia.