Table 3. Overview of outcomes of the included studies.

First Author, Date, Country	Design	Participants	Mean age (SD) / (Male %)	Intervention and Control	Setting, Intervention programme	Intervention length, delivery modality and support/guidance provided	Measure depression/anxiety/stress at baseline and theoretical underpinning of methods, ITT or PP analysis	Results (Intervention vs. Control) Mean (SD), significance	Summary
Employees with general levels of psychological distress
Billings et al., 2008 [43], USA	RCT	Employees from a technology company in USA	34 (SD not reported), Male (29.4%) mean score, SD PHRQ	Web-based n = 154; wait-list control n = 155	Technology company, CBT based Stress and Mood Management, use of embedded assessment and multimedia elements	3 month web-based, multimedia health promotion program which is tailored to the individual user through baseline assessment, no guidance or support indicated Fu = 3 months	Not measured. No theory PP	1)Anxiety (BAI) 3M: NS 2) Depression(CES-d) 3M: NS 3)Stress (SDS) B: 17.52 (4.53) vs 16.81(3.78) 3M: 16.03(4.18) vs.16.5(4.35), p = 0.023	Stress related measures improve significantly. Anxiety and depression did not improve.
Bolier et al., 2014 & Ketelaar et al., 2013 [48,49], Netherland	Cluster RCT	Nurses and Allied Health Professionals	40 (12), Male (21.2%)	Workers’ health surveillance module (WHS)online intervention n = 178, wait-list no intervention control n = 188	Hospital wards, Range of CBT-based interventions targeting mental fitness; work stress; depressive and panic symptoms and risky drinking behaviour offered following screening	3 month intervention period programmes delivered via website. Feedback provided following screening, access to contact forum provided. Fu = 6 months	Not measured. No theory PP	1) Anxiety (BSI)§ 6M: NS 2) Depression (BSI)§ 6M: NS 3)Stress (IES)§ 6M:NS (subgroup with high stress levels only) 4)Well-being Index (WHO-5)§ 6M: NS 5)Mental Health Continuum- Short Form (MHC-SF)§ B:3.39 (0.66) vs.3.25 (0.74) 6M:3.65 (0.66) vs. 3.33 (0.74), p = 0.03 (cohen’s d = 0.37 at 3 months and 0.28 at 6 months)	No significant improvements in anxiety, depression, and posttraumatic stress. Positive mental health was significantly enhanced in the intervention group, in comparison to the control group
Bostock et al.,✴ 2016 [47], UK	RCT	Employees from a Global ’Fortune 500 ’company who were self-identify as having poor sleep	34(6.01), Male (67%)	digital Cognitive Behavioural Therapy (dCBT) n = 135, wait list control n = 135	Worldwide corporations, CBT based programme is is presented by an animated virtual therapist (‘The Prof’), and tailored by the programme’s algorithms to each individual’s characteristics, personal goals, sleep diary data and progress	8 week digital Cognitive Behavioural Therapy (dCBT) for insomnia was delivered via an established program (www.sleepio.com and associated Sleepio App); No support or human contact. Fu = 8 weeks	Not measured. No theory PP	1)Anxiety 8wk: NS 2) Depression 8wk: NS 3) Sleep Condition Indicator(SCI) B:4.78 (0.14) vs.4.72 (0.14) 8wk: 6.44 (0.16) vs. 6.44 (0.16), Cohen’s d = 1.10 vs 0.34, p<0.0001	No significant improvement for depression or anxiety. Significant improvement for sleep.
Weber et al., 2019 [46], Germany	RCT	Employees from six different businesses in the European countries	41 (11.19), Male (24%)	mHealth n = 210, wait list control n = 322	Various organisations, Kelaa mental Resilience App based on CBT and mindfulness based cognitive therapy	4 weeks intervention (maximum of 28 sessions); personalised feedback on questionnaire scores as well as detailed feedback on sleep data are given within the app. Fu = 6 weeks	Not measured. JDR (job demands-resources model of burnout) PP	1a) Stress, General (COPSOQ II)§ B: 3.00 (0.76) vs. 3.01 (0.73) 6 wk: 2.46 (0.80) vs. 2.57 (0.81), p <0.001 1b) Stress, Cognitive (COPSOQ II)§ B:2.59 (0.85) vs. 2.63 (0.78) 6wk: 2.17 (0.85) vs. 2.34 (0.81), p < 0.01 2) Insomnia (COPSOQ II)§ 6wk: NS 3) Wellbeing(WEMWBS)§ B: 3.26 (0.65) vs. 3.23 (0.60) 6wk: 3.45 (0.78) vs. 3.44 (0.71), p < 0.01	Significant improvement in stress and wellbeing but not insomnia.
Employees with higher levels of psychological distress
First Author, Date, Country	Design	Participants	Mean age (SD) / (Male %)	Intervention and Control	Intervention programme	Intervention length, delivery modality and support/guidance provided	Measure depression/anxiety/stress at baseline and theoretical underpinning of methods, ITT or PP analysis	Results (Intervention vs. Control) Mean (SD)	Summary
Ebert et al., 2016 [44], Germany	RCT	Employees from an insurance company with PSS-10 scores ≥22	42 (9), Male(28%)	Internet-based stress management intervention (iSMI) n = 131 or wait list control n = 132	Insurance company, GET.ON Stress’ CBT programme, problem-solving and emotional-regulation strategies	7 week (7 sessions) self-guided programme delivered via website and mobile device. Content was tailored to each participant’s response. No human support. The participants could choose to receive automatic motivational text messages and small exercises on their mobile phones. Fu = 6 months	Only included participants with scores ≥22 on the Perceived Stress Scale (PSS-10). Lazarus and Folkman ’ Transactional Model of Stress’ ITT	1)Anxiety (HADS-A) B;11.4(3.4) vs. 11.3(3.6) 7wk: 8.0(3.7) vs 9.9(3.8), p<0.001 6M: 7.2(3.7) vs. 9.3(4.2), p<0.001 2) Dépression(CES-D) B: 25.1(9.31) vs. 23.9(8.3) 7wk: 16.1(8.7) vs 21.4(9.1), p<0.001 6M: 15.2(9.0) vs 20.2(10.0), p<0.001 3) Stress (PSS-10) B: 25.7 (5.0) vs. 26.1 (4.1) 7wk: 18.1(5.7) vs. 23.4(5.4), p<0.001 6M: 17.5(6.7) vs. 21.8(6.7), p<0.001 4) Insomnia Severity(ISI) B: 13.0(5.6) vs. 12.8(6.0) 7wk: 9.3(5.2) vs. 11.2(6.5), p<0.001 6M: 8.0(5.1) vs. 10.3(6.0), p<0.001	Improvement of sleep, anxiety, depression and stress
Volker et al.,✴ 2015 [50], Netherland	Cluster RCT	Sick-listed employees with common mental disorders who were on sickness absence between 4 and 26 weeks and screened positive (score ≥10) on either PHQ-9 and/or PHQ-15 and/or GAD-7	45 (10), Male (40%)	E-health module embedded in Collaborative Occupational health care (ECO)n = 131, Care as usual n = 89	Various companies, Return@Work’ Pyscho-education, CBT, problem-solving, pain/fatigue management and relapse prevention.	5 modules (up to 16 sessions, tailored to individual) over 3 months combined with occupational physician consultations who received automated email that were based on decision aid. Fu = 12 months	Only included participants who screened positive (score ≥10) on either the depression scale of the PHQ-9 and/or the somatization scale of the PHQ-15 and/or the GAD-7. No theory ITT	1)Anxiety (GAD7) 3M, 6M, 9M, 12M: NS 2) Depression (PHQ9) 3M, 6M, 9M, 12M: NS 3)Somatisation (PHQ15) B:12.54(4.3) vs. 13.03 (4.9) 9M: 8.45 (5.1) vs. 10.11 (4.9), p = 0.017 12M:8.01 (5.04) vs. 9.47 (5.2), p = 0.039 3M and 6M: NS	No significant difference in depression and anxiety between intervention and control. But significant improvement in stress/somatisation related physical symptoms at 9 and 12 months
Grime, 2004 [45], UK	RCT	Employees from the London NHS occupational health department who were on sick leave for 10 or more cumulative days due to stress, anxiety or depression in the past 6 months, and scored ≥ 4 on GHQ-12	39 (9), Male (42%)	‘Beating The Blues’ plus conventional care n = 24, conventional care n = 24	London NHS occupational health department, Beating The Blues’ computerised CBT programme aims to challenge specific thinking patterns and implement behavioural change. It concludes with a therapy map or programme review, goal setting and action planning.	8 weeks (8 sessions) CBT programme was loaded onto a standalone computer in a private room in the occupational Health Department.; all participants received conventional care. Fu = 8 weeks	Only included participants who scored 4 or more on the GHQ-12 (General Health Questionnaire). No theory PP	1)Anxiety (HADS) B: 11.75(3.87) vs. 14.04 (4.34), 1M:8.20(3.95) vs. 12.00 (3.61), p = 0.021 End of treatment, 3M and 6 M: NS 2) Depression (HADS-D) B: 7.96 (3.43) vs. 10.63 (4.13) End of treatment:: 5.38 (3.93) vs. 8.61 (3.86), p = 0.028 1 M: 5.00 (3.32) vs. 8.53 (3.82), p = 0.040 3M and 6M:NS	Significant improvement in depression and anxiety at 1 month after the end of treatment but not 3 and 6 months follow up.

✴results were provided by the study authors, § = group*time interaction. B = baseline, Fu = follow up, NS = Non-significant, ITT = Intention to treat, PP = Per protocol Only significant differences are shown.

SDS = Symptoms of distress scale BAI = Beck Anxiety Inventory CES-D = Center for Epidemiological Studies BSI = Brief Symptom Inventory ISI = Insomnia Severity Index HADS-A = Hospital Anxiety and Depression Scale

PSS-10 = Perceived Stress Scale GAD-2 = Generalised Anxiety Disorder-2 item, COPSOQ II = Copenhagen Psychosocial Questionnaire–Revised Version(general stress) WEMWBS = Warwick-Edinburgh Mental Wellbeing Scale WHO-5 = WHO Well-being Index IES = Impact of Event Scale SCI = Sleep Condition Indicator PHQ-9 = Patient Health Questionnaire-9 PHQ-15 = Patient Health Questionnaire-15

GAD-7 = Generalised Anxiety Disorder-