Abstract: Objective To investigate the efficacy and safety of transcranial alternating current stimulation (tACS) in the treatment of primary insomnia complicated by anxiety. 
Methods Sixty-two patients with primary insomnia were randomly divided into treatment group and control group. The patients in the treatment group received real tACS while the patients in the control group were treated with sham tACS. The treatment session was 20 times in both groups. The treatment site was prefrontal and bilateral mastoid regions, with a frequency of 77.5 Hz and an intensity of 15 mA. Pittsburgh sleep quality index (PSQI) and Hamilton Anxiety Scale (HAMA) were used to evaluate the clinical symptoms at baseline, and at the end of treatment (4 weeks) and follow-up (8 weeks). Adverse reactions were assessed using Treatment Emergent Symptom Scale and recorded. 
Results The scores of PSQI and HAMA in the treatment group and the control group at baseline, 4 weeks after treatment and 8 weeks after follow-up were compared using repeated measurement analysis of variance. The total scores of PSQI and HAMA in the two groups decreased gradually with the extension of treatment and follow-up time (Ptime＜0.05). The decrease in the treatment group was greater than that in the control group (Pgroup＜0.05), and the effect of treatment increased with the extension of observation time (Pinteraction＜0.05). The total score of HAMA in both groups decreased gradually with the extension of treatment and follow-up time (Ptime＜0.05), and the effect of treatment increased with the extension of observation time (Pinteraction＜ 0.05); However, there was no significant difference between two groups (Pgroup＞0.05). 
Conclusion tACS is effective and safe in the treatment of primary insomnia complicated by anxiety. It can be used as a new option for the treatment of primary insomnia, especially for those patients with anxiety. 

Key words: sleep disorders, electric stimulation therapy, anxiety