Bernburg 2020.

Study characteristics
Methods	Study design: randomised controlled trial Study grouping: parallel group
Participants	Baseline characteristics Psychosocial competence training combined with cognitive behavioural and solution‐focused counselling Age (mean ± SD): 23.1 ± 2.5 Sex (N (% female)): 36 (78%) Sample size: 47 Years of experience (mean ± SD): 1.3 ± 1.1 Control (no intervention) Age (mean ± SD): 23.6 ± 2.4 Sex (N (% female)): 33 (71%) Sample size: 47 Years of experience (mean ± SD): 1.2 ± 1.3 Overall Age (mean ± SD): 23 ± 2.5 Sex (N (% female)): 69 (73%) Sample size: 94 Years of experience (mean ± SD): 1.1 ± 1.3 Included criteria: Inclusion criteria were: (1) regular access to the Internet, (2) full‐time employment in a clinic, (3) a maximum of two years of work experience (junior nurse), (4) availability and willingness to participate during the 36 weeks, (5) agree to complete the questionnaires, (6) no previous knowledge or experience with mental health promotion training. Excluded criteria: NR Pretreatment: Baseline data on socio‐demographic differences indicated only small, insignificant differences between intervention and control group (P > 0.05). Not recorded whether groups differed at baseline on the primary outcome perceived stress. Compliance rate: NR Response rate: difficult to assess as figure 1 is mentioned but not included in the article. Type of healthcare worker: exclusively junior nurses
Interventions	Intervention characteristics Psychosocial competence training combined with cognitive behavioural and solution‐focused counselling Type of the intervention: Intervention type 4 ‐ Combination of two or more of the above Description of the intervention: Training sessions included theoretical input, watching videos, oral group discussions, experiential exercises, and home assignments. Module: Psycho‐educational information. During the first session, the nurses received psycho‐educational information about stress based on Lazarus’ transactional model of stress and basic information on stress. This session was designed to prepare nurses with general knowledge of coping methods (emotion‐focused and problem‐focused coping strategies) and more specific coping strategies for work‐related problematic situations. Subsequently, the nurses identified personal goals, work‐related stressors, and motivation for training participation. Module on problem‐solving techniques. In sessions 2 and 3, the nurses worked on problem‐solving techniques. This module was based on solution‐focused therapy. The participants learnt a systematic six‐step problem‐solving method that can be applied to an individual’s problems. Typical scenarios for work‐related stress in hospitals were presented. Module on techniques of emotion regulation ‐ The nurses worked on modules for emotion control and emotion regulation. Techniques include muscle and breath relaxation, acceptance and tolerance of emotions, and effective self‐support. The techniques were presented using examples of emotional reactions related to the typical work context. Module for planning for the future ‐ The participants were asked to develop a plan for the future. They were also asked to strengthen something important in their lives and to imagine life after completion of the training modules. The number of sessions: 12 Duration of each session on average: 1.5 hours Duration of the entire intervention: 12 weeks Duration of the entire intervention short vs long: Long Intervention deliverer: Two qualified psychotherapists conducted the training sessions. Both psychotherapists were registered and accredited as psychotherapists. They had training in cognitive behavioural therapy, systemic therapy, and solution‐focused brief therapy Intervention form: Group, face‐to‐face Control (no intervention) Type of the intervention: NA Description of the intervention: The CG group received no intervention on mental health and did not undertake anything comparable to the intervention, e.g. any other training in psychosocial skills, counselling or therapy The number of sessions: NA Duration of each session on average: NA Duration of the entire intervention: NA Duration of the entire intervention short vs long: NA Intervention deliverer: NA Intervention form: NA
Outcomes	Perceived Stress Questionnaire (PSQ) Outcome type: ContinuousOutcome Maslach Burnout Inventory ‐ Emotional Exhaustion Outcome type: ContinuousOutcome
Identification	Sponsorship source: NR Country: Germany Setting: Hospitals Comments: NA Authors name: Monika Bernburg Institution: Institute of Occupational Medicine, Social Medicine and Environmental Medicine, Goethe University, Germany Email: s.mache@uke.de Address: Address for correspondence: Stefanie Mache, Institute for Occupational Medicine and Maritime Medicine (ZfAM), University Medical Center Hamburg‐Eppendorf, Martinistraße 52, 20251Hamburg, Germany. Time period: NR
Notes	MBI‐EE included in analysis 4.1 and 4.2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "After answering the baseline questionnaire (t0) participants were randomized with the ratio 50%: 50% to the two study groups (IG or CG). The randomization process was accomplished with a computer generated list of numbers."
Allocation concealment (selection bias)	Low risk	Quote: "This list was created by an independent research assistant; another assistant was blinded to the list, securing covered distribution to research conditions."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "The CG group was asked to complete all surveys. The CG group received no intervention on mental health and did not undertake anything comparable to the intervention, e.g. any other training in psychosocial skills, counselling or therapy." Participants were not blinded.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Participants were not blinded whereas outcomes are self‐reported.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Dropout attrition: There was an overall drop‐out rate (from randomization to analysis) of 12%. 10 participants decided to terminate the study (reasons included illness, non‐appearance of participants) and did not answer the questionnaires. Overall, four of the 94 participants at T1, 6/94 of participants at T2 and 4/94 of participants at T3 did not provide all follow‐up data on the results. The participants who did not provide all follow‐up data did not differ in any meaningful way, either in the primary outcome or in other baseline outcomes (P > 0.05), from those who provided data. " Low loss to follow‐up and follow‐up seems to be at random.
Selective reporting (reporting bias)	Unclear risk	No trial registration or no study protocol reported, nor did we find one online
Other bias	Unclear risk	Compliance rate not reported and response rate difficult to assess. Not recorded whether groups differed at baseline on the primary outcome perceived stress.