Study registration
This systematic review and meta-analysis protocol was registered on PROSPERO with a registration number of CRD 42024610457. This study was designed and conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines19.
Search strategy
A comprehensive literature review was conducted by two authors (XXZ and JZ), who searched the Cochrane Library, Ovid Embase, Ovid MEDLINE, PubMed, Scopus, and Web of Science Core Collection databases. Their search encompassed all relevant records from the start of each database's coverage up to June 30, 2024.
The search strategy employed a combination of controlled vocabulary (e.g., MeSH) and free-text terms pertaining to digital health interventions, depression, anxiety, and stress. To maximize the retrieval of pertinent studies, Boolean operators (AND, OR) were utilized. The search was restricted to publications in the English language. The complete search strategy is detailed in eTable 1 in Supplement 1. Citation Chaser was used to search the reference lists of the included studies and to retrieve articles that had cited the included studies to find additional relevant studies20.
Study selection and inclusion criteria
The inclusion and exclusion criteria for this systematic review were defined according to the Population, Intervention, Comparison, Outcomes, Study Design (PICOS)19 framework: Population (P): Studies involving university students, regardless of age, gender, or field of study. Intervention (I): Any digital health intervention primarily delivered via the internet or a mobile device and aimed at alleviating symptoms of stress, anxiety, or depression. This included, but was not limited to, web-based programs, mobile apps, and chatbot-delivered therapies. Comparison (C): Control groups including wait list controls, active controls (e.g., receiving nondigital psychoeducation), treatment as usual, or other digital health interventions. Outcomes (O): Studies had to report outcomes on at least one of the following, measured using a validated scale: stress (e.g., Perceived Stress Scale, PSS), anxiety (e.g., GAD-7), or depression (e.g., PHQ). Study Design (S): Only randomized controlled trials (RCTs) were included to ensure the highest quality of evidence.
Upon completion of the database search and duplicate removal, the titles and abstracts of the identified records were screened independently by two authors (XXZ and JZ). Any discrepancies encountered were adjudicated by a third reviewer (DZ). Subsequently, the full texts of the remaining articles were assessed for eligibility by two other independent reviewers (DZ and YFC), with a third reviewer (JZ) serving as an arbiter to reach a consensus on final inclusion.
The inclusion criteria encompassed all digital health intervention types (e.g., web-based programs, mobile applications) to facilitate a comprehensive analysis and direct comparison across technological modalities. Studies were required to report outcomes related to stress, anxiety, or depression using validated measurement scales. Studies were excluded if they possessed the following characteristics: lack of assessment of the relevant variables, population outside the intended scope, review articles, abstracts, editorials or letters, animal studies, or case reports. Studies that reported insufficient data for calculating effect sizes, even after attempts to obtain it from the authors, were excluded from the meta-analysis. Conference abstracts were excluded due to the lack of detailed information and in-depth methodology required for a robust assessment of quality and data extraction. Citations from all the databases were imported into an EndNote X21 library (Clarivate Analytics).
Appraisal of methodical quality
The quality of the included RCTs was independently assessed by two authors (DZ and YFC) according to the guidelines of the Cochrane reviews21. The evaluation contents include (1) random sequence generation, (2) allocation concealment, (3) blinding of participants and personnel, (4) blinding of outcome assessment, (5) incomplete outcome data, (6) selective reporting, and (7) other types of bias. Each included study was judged to have a "low", "high", or "unclear" risk of bias for each domain. If the researchers scored the four criteria as "low" and if no serious flaws were detected, then the study was scored as having a low risk of bias.
Extraction of the data
The following data from eligible studies were independently extracted by two authors (JZ and DZ): authors, year of publication, country, participant characteristics (including age, sample size, and distribution of groups), assessment tools employed for depression, anxiety, and stress, digital health interventions (delivery mode, treatment length, control group, intention to treat, attrition rate), and the related statistical data. The procedure for handling missing data (e.g., standard deviations) involved attempting to contact the corresponding authors twice within a four-week period. If no response is received, then SDs will be calculated from standard errors, confidence intervals, or P values provided in the studies, following the methods outlined in the Cochrane Handbook21. Any discrepancies or inconsistencies in the extracted data were resolved through discussion between the two reviewers (JZ and DZ). If a consensus could not be reached, then a third reviewer (XXZ) was consulted to make the final decision.
Data synthesis
For each outcome, the quantitative data were synthesized and are presented as the weighted mean difference (WMD) with a corresponding 95% confidence interval (CI). The WMDs were calculated by pooling the pre-to-post change scores (mean and SD) extracted from each eligible study. Heterogeneity across studies in direct comparisons was assessed using the I2 statistic, with values of 25%, 50%, and 75% conventionally denoting low, moderate, and high heterogeneity, respectively. A fixed effects model was applied when heterogeneity was not significant (I2< 50% and P > 0.1); otherwise, a random-effects model was employed.
The results were visualized using forest plots, which display the first author's name, publication year, sample size, effect estimate with its 95% CI, and associated P value for each study. Subgroup analyses were performed separately for each primary outcome (stress, anxiety, and depression). For each outcome, the analyses were stratified by the specific measurement instrument used (e.g., for stress: Connor-Davidson Resilience Scale (CD-RISC)22, Brief Resilience Scale (BRS)23, Perceived Stress Scale (PSS)24, Depression Anxiety Stress Scale (DASS)-Stress subscale25,26,27; for anxiety: Generalized Anxiety Disorder Scale (GAD)28, State-Trait Anxiety Inventory (STAI), DASS-Anxiety subscale27,29; for depression: Patient Health Questionnaire (PHQ)30, Beck Depression Inventory (BDI)31, DASS-Depression subscale26,27). Other subgroup variables included the following: (1) intervention technique: web- or app-based cognitive-behavioral therapy (CBT), mindfulness-based intervention (MBI), physical-activity intervention (PAI), and other psychological intervention (OPI) excluding CBT, MBI, and PAI; (2) guidance format: reminder only, feedback only, mixed (reminder + feedback), or none; (3) delivery mode: smartphone app, web-based platform/program, or other; (4) treatment duration: ≤ 4 weeks, > 4 to < 8 weeks, or ≥ 8 weeks; (5) recruitment pathway: online, mixed, on-campus, or unspecified; and (6) control group type: active or passive. Passive controls receive no intervention as they serving to control for the natural history of the condition and placebo effects. In contrast, active controls receive an alternative, standard, or placebo intervention to control for nonspecific effects of the intervention process. The assessment of publication bias involved examining funnel plot asymmetry and performing Egger's regression test. Bias was considered to be present if visual asymmetry was accompanied by a significant Egger's test result (P < 0.05). Egger's test was conducted solely for outcomes with 10 or more studies to ensure the test's power32. The primary data analysis, including the generation of forest and funnel plots, was performed using Review Manager (RevMan) version 5.3 software. Additionally, Stata version 18 was used to conduct the statistical assessment for publication bias (Egger's test).