Table 4.

Electrical stimulation therapies for insomnia.

Therapy	Evaluation item	Evaluation results
tES (tACS/tDCS)	Representative Study Design	Literature	Population	N	RCT	Placebo effect excluded	Objective biomarkers	Follow-up
		(130)	(b) adults with sleep-onset insomnia symptoms	24	Yes	Partly yes	Yes	No
		(131)	(a) diagnosed by DSM-5	54	Yes	No	No	Yes
		(174)	(a) diagnosed by ICD-11	157	Yes	No	No	Yes
	Main Clinical Findings & Safety	Mixed but partly positive sleep effects; may improve PSQI, SE, TST, or SOL. Mostly tolerable, but one high-current study raised safety concerns (133).
	Limitations	Small samples; heterogeneous protocols; limited objective data/follow-up; sham/blinding and reporting issues.
	Evidence Level	Emerging. Promising but inconsistent evidence; insufficient for routine clinical use.
taVNS	Representative Study Design	Literature	Population	N	RCT	Placebo effect excluded	Objective biomarkers	Follow-up
		(134)	(a) diagnosed by DSM-5	72	Yes	Yes	No	Yes
		(135)	(a) diagnosed by ICSD-3	40	Yes	Yes	Yes	No
		(143)	(a) diagnosed by DSM-5	67	Yes	Yes	No	No
	Main Clinical Findings & Safety	taVNS improved sleep quality/insomnia severity and some sleep parameters; adverse events were rare, mild, and manageable (132, 144).
	Limitations	Small samples, heterogeneous protocols, short follow-up, mostly subjective outcomes, and bias concerns.
	Evidence Level	Emerging. Benefits are suggested, but certainty remains low/very low; larger sham-controlled RCTs are needed.
Neurofeedback Biofeedback	Representative Study Design	Literature	Population	N	RCT	Placebo effect excluded	Objective biomarkers	Follow-up
		(136)	(a) diagnosed by DSM-4	82	No	No	Yes	No
		(137)	(a) diagnosed by DSM-5	17	Yes	No	Yes	Yes
		(138)	(c) cancer patients	28	Yes	No	Yes	No
	Main Clinical Findings & Safety	Possible sleep benefits in small studies, but surface neurofeedback did not outperform controls for insomnia/sleep quality (139). Stress biofeedback improved stress/anxiety/depression (140). No major safety concerns reported.
	Limitations	Small samples, heterogeneous protocols, limited sham controls, mostly self-report, short/unclear follow-up, indirect populations.
	Evidence Level	Emerging. Some supportive controlled/meta-analytic data, but insomnia-specific efficacy is inconsistent and limited by bias, heterogeneity, and weak long-term evidence.
HVET	Representative Study Design	Literature	Population	N	RCT	Placebo effect excluded	Objective biomarkers	Follow-up
		(148)	(b) adults	100	No	No	No	No
		(149)	(b) adults	40	No	No	No	No
		(150)	(a) Chinese Guidelines for the Diagnosis and Treatment of Adult Insomnia, 2017 edition	88	Yes	No	No	No
	Main Clinical Findings & Safety	Studies suggest improved PSQI/sleep quality; one add-on RCT also reported fewer adverse events. No major safety issues reported.
	Limitations	Small, short-term; limited randomization; no sham control; subjective outcomes only; no follow-up.
	Evidence Level	Exploratory. Evidence is mainly small/limited clinical data without adequate controlled validation.