LAUSR

Chronic insomnia is one of the most common types of sleep disorder [1]. The incidence of chronic insomnia in the general population ranges from 4% to 48% [2]. Because of its high prevalence and increased incidence, it has become a vital public health problem. Chronic insomnia increases the risk of mental and physical illness and of drug dependence or abuse [3]. At present non-drug therapy and drug therapy are usually used to treat chronic insomnia. Many patients with chronic insomnia have to take sedative hypnotic drugs for a long time to maintain sleep, and long-term use of drugs will bring a series of side effects and adverse reactions [4]. Therefore, it is necessary to find new effective non-drug treatments to improve the quality of sleep of chronic patients. Transcranial alternating current stimulation (tACS) is a lowintensity non-invasive transcranial electrical stimulation (CES) method. tACS regulates the excitability of the cerebral cortex and brain function by affecting the synchronization and desynchronization of the electrical activity of brain nerve cells [5]. Recently, it was introduced into clinical treatment trials for neuropsychiatric diseases. tACS is non-invasive, easy to perform, inexpensive, and safe, which gives the technology certain development potential in the medical field. The application of tACS in depression found that after the initial study, patients responded to treatment, but their condition did not significantly improve [6]. This was followed by a further extension of the previous clinical trial, in which one participant received an additional 12 rounds of 10-Hz tACS treatment every week, and the participant's condition was relieved after treatment [7]. Although the study was conducted in a single participant, it may support the feasibility of long-term tACS as a potential safety tool in MDD treatment studies. Based on the status of the aforementioned studies, the randomized double-blind clinical trial reported herein is the first to study the efficacy and safety of tACS in the treatment of adult patients with chronic insomnia [8]. This study was conducted on adult patients with chronic insomnia at the Neuromodulation Laboratory, Department of Neurology, Xuanwu Hospital of Capital Medical University (China). The inclusion criteria were as follow: (1) 18e65 years old; (2) diagnosis of chronic primary insomnia; (3) difficulty falling asleep, difficulty remaining asleep, difficulty waking up in the morning, or any combination of these for more than 3 nights a week going back more than 3 months; (4) severely impaired daytime function; (5) baseline sum score of PSQI > 8; (6) no use of hypnotics or insomnia drugs for at least 4 weeks before the baseline visit; (7) consent to use birth control during the study period (among female patients aged 18e50 years); and (8) agreement not to receive drug therapy