Jiang B, et al. - In view of the accepted knowledge that placebo effects have been significant in insomnia clinical trials, researchers sought to characterize the dynamic features of placebo effects addressing persistent insomnia disorder via performing a meta-analysis of placebo-controlled randomized clinical trials. Randomized, placebo-controlled, double-blind clinical trials estimating the efficacy of therapeutic regimens addressing persistent insomnia disorder were assessed for pooling separate effect size estimates (Hedge's g) of placebo and regimen conditions. Outcomes revealed significant and robust placebo effects for improving the symptoms of insomnia; they identified significantly smaller subjective measures vs objective measures, but nearly identical placebo response rates between subjective and objective measures. Publication year, treatment duration, sample size, and therapeutic regimen were identified influencing the overall placebo effects. Within treatment duration, a diphasic feature of placebo effects was observed: initially a decrease and subsequently being stable; a sustained decline trend after withdrawals; and a steady-to-upward trend for mixed therapeutic regimens in a large-scale period over decades. The development and validation of dosing strategies that require less medication exposure to maintain clinical effects may be possible with assessing the dynamic features of placebo effects addressing persistent insomnia disorder.