A 52-year-old male with major depressive disorder and comorbid chronic insomnia presents for medication management. He has been on sertraline 150 mg daily for 8 weeks with partial improvement in mood but persistent difficulty with sleep onset and maintenance. He reports no history of substance use disorder, obstructive sleep apnea, or restless leg syndrome. The PMHNP considers adding trazodone at a low dose. Which of the following best explains the pharmacologic rationale for using low-dose trazodone as a sleep aid in this patient?