Background <p>Although the 3P model outlines key psychological contributors to insomnia, it remains unclear which factors are most central or mechanistically relevant. This study aimed to identify key psychological factors within the 3P framework using network analysis (Study 1), and to examine their associations with objective sleep parameters (Study 2).</p> Method <p>A total of 369 patients with insomnia disorder (ID: mean age = 30.94 ± 11.36 years) and 207 healthy controls (HC: mean age = 29.92 ± 10.42 years) were recruited from outpatient clinics and community settings. Participants completed questionnaires assessing demographic and psychological variables related to insomnia. Additionally, a portable single-channel EEG device was used to record whole-night sleep at home. Network analysis was used in Study 1, and regression analysis was used in Study 2.</p> Results <p>Network analysis revealed that trait anxiety, cognitive arousal, and rumination were the most central nodes in the ID network. No significant differences were observed between ID and HC in network structure, global strength, or individual edge strengths after Holm-Bonferroni correction. Study 2 demonstrated that longer REM latency was significantly associated with greater cognitive arousal (<i>β</i> = 0.152, <i>p</i> = 0.04), while shorter total sleep time was associated with higher rumination (<i>β</i> = − 0.183, <i>p</i> = 0.012) in ID.</p> Conclusions <p>Cognitive arousal emerged as a central factor in insomnia and was found to be associated with REM latency. Integrating subjective and objective measures provides a comprehensive understanding of the cognitive mechanisms underlying insomnia and highlights cognitive arousal as a potential intervention target.</p>