TABLE 1.

Characteristics of studies included in the review.

Author, year, location	Study design	Sample size randomised (female), mean age (SD), recruitment	Hypnotic medication status, comorbidity	Diagnostic criteria of insomnia (determined by)	Intervention & its format	Control	Depression measure (PT, FU)	Risk of bias
Kyle et al. (2023), UK	RCT	N = 642 (489 f) SRT (n = 321): 55.7 years (15.3) SHE (n = 321): 55.2 years (16.5) Adults from medical practices	Medication allowed, psychiatry comorbidity allowed	DSM‐5 Insomnia Disorder (SCI)	4‐session SRT Individual, FtF (S1, S3), Phone (S2, S4)	SHE	PHQ‐9 (3 m, 6 m, 12 m)	Some risk of bias
Maurer et al. (2020), UK	RCT	N = 56 (39 f) SRT (n = 27): 40.63 years (9.13) TBR (n = 29): 40.93 years (9.24) Adults from community	Medication free, psychiatric comorbidity excluded	DSM‐5 Insomnia Disorder (SCI ≤ 16 and telephone interview)	4‐week SRT Individual, FtF (1, 2 week), Phone (3, 4 week)	TBR	HADS‐D (4 wk, 3 m)	Some risk of bias
Krieger et al. (2019), Switzerland	RCT	N = 62 (45 f) SRT (n = 41): 46.59 years (17.52) CAU (n = 21): 45.24 years (12.40) Adults from physician referrals and community	Medication allowed, psychiatric comorbidity excluded	ICSD‐3 Insomnia Disorder (Telephone interview)	8‐week SRT Internet‐based, one session per week	CAU	ADS‐K (8 week, 6 m)	High risk of bias
Kalmbach (2019), USA	RCT	N = 102 (102 f) SRT (n = 52): 56.65 years (4.95) SHE (n = 50): 57.34 years (5.97) Postmenopausal women from primary care, sleep clinic and community	Medication free, depression comorbidity excluded	DSM‐5 Insomnia Disorder Self‐reported WASO of ≥ 1 hr on ≥ 3 nights per week; objective WASO of ≥ 45 min (Clinical interview & 2 nights of PSG)	2‐week SRT Individual, FtF (initial & ending session), phone (every 3–4 days between 1 and 2 weeks)	SHE	BDI‐II (4 week, 6 m)	High risk of bias
Gieselmann (2019), Germany	RCT	N = 49 (25 f) SRT (n = 27): 39.3 years (14.47) WLC (n = 22): 42.74 years (11.73) Adults from medical practice, university and community	Medication allowed, psychiatric comorbidity allowed	Insomnia disorder SOL of > 30 min for ≥ 3 nights per week over the last 6 months (Clinical interview)	3‐week SRT (combined with imagination exercise and sleep hygiene advise), individual, FtF (1, 3 weeks)	WLC	CES‐D (4 week, 2 m)	High risk of bias
Falloon (2015), New Zealand	RCT	N = 97 (75 f) SSR (n = 46): 55.4 years (12.7) SHE (n = 51): 51.8 years (13.4) Adults from general practices	Medication free, psychiatric comorbidity excluded	Insomnia disorder for ≥ 6 months Sleep difficulties on ≥ 3 nights per week (Questionnaires, physical examination, sleep diary at baseline)	3‐week SSR Individual, FtF (1, 3 weeks)	SHE	PHQ‐9 (/, 6 m)	High risk of bias
Epstein (2012), Canada	RCT	N = 94 (57 f) SRT (n = 44): 68.00 years (8.25) WLC (n = 50): 69.50 years (8.34) Older adults from community	Medication free, psychiatric comorbidity excluded	Insomnia Disorder for ≥ 6 months sleep onset or maintenance of ≥ 45 min per night for ≥ 3 nights per week; Complained of impaired daytime functioning (2‐week sleep diary at baseline)	6‐week SRT (with sleep hygiene instructions), Group (4–6 individuals), FtF (1, 2, 4 weeks), Phone (5–6 weeks)	WLC	GDS (6 week, /)	High risk of bias
Aji (2020), Australia	UCT	N = 15 (15 f) 40.0 years (14.2) Adults from clinician referrals and community	Medication free, severe psychiatric comorbidity excluded	DSM‐5 Insomnia Disorder (ISI ≥ 15, PSQI > 5, clinical interview)	3‐week SRT Mobile app	/	HADS‐D (6 week, /)	/
Lancee (2019), Netherlands	UCT	N = 7 (4 f) 45.7 years (range 28–69) Adults from community	Medication free, insomnia with depressive symptoms, psychiatric comorbidity allowed	Insomnia disorder (SCID‐5‐RV, ISI ≥ 10, SE ≤ 85, clinical interview)	6‐week SRT Individual, FtF (1, 3 weeks), phone (2, 4, 5, 6 weeks)	/	PHQ‐9 & BDI‐II (6 week, 3 & 6 m)	/

Abbreviations: ADS‐K, Allgemeine Depressions‐Skala – Kurzform (German version of CES‐D); BDI‐II, Beck Depression Inventory II; CAU, care as usual; CES‐D, Center for Epidemiological Studies Depression Scale; DSM‐5, Diagnostic and Statistical Manual of Mental Disorder, Fifth Edition; FtF, face to face; FU, follow‐up; GDS, Geriatric Depression Scale; HADS‐D, Hospital Anxiety and Depression Scale – Depression Subscale; ICSD‐3, International Classification of Sleep Disorders, Third Edition; ISI, Insomnia Severity Index; PHQ‐9‐D, Patient Health Questionnaire – Depression Scale; PSG, polysomnography; PSQI, Pittsburgh Sleep Quality Index; PT, post‐treatment; RCT, randomised controlled trial; SCI, sleep condition indicator; SCID‐RV, Structured Clinical Interview for DSM‐5 – Research Version; SE, sleep efficiency; SHE, sleep hygiene education; SOL, sleep‐onset latency; SRT, sleep restriction therapy; SSR, simplified sleep restriction; TBR, time in bed regularisation; UCT, uncontrolled clinical trial; WASO, wake after sleep onset; WLC, wait list control; S, session; m, month.