Efficacy of standalone smartphone apps for mental health: an updated systematic review and meta-analysis

To map out the potential benefits of widely available smartphone apps for mental health, especially in contexts where face-to-face services are limited or unavailable, it is crucial to examine their efficacy compared with inactive controls. Standalone smartphone apps might offer an accessible option for individuals waiting for treatment or living in under-resourced settings. Given the currently inconclusive evidence regarding these apps, this systematic review and meta-analysis aimed to assess the efficacy and study quality of randomised controlled trials (RCTs) evaluating standalone smartphone apps for mental health.

In this systematic review and meta-analysis, based on a previously published study, we conducted an updated systematic search of PubMed, PsycINFO, Web of Science, Cochrane Clinical Trial, and Scopus for RCTs published from database inception to Nov 10, 2023. We included RCTs that examined the efficacy of standalone smartphone apps for mental health in adults (age ≥18 years) with heightened symptom severity compared with an inactive control group (eg, waitlist, informational material, and control apps). We excluded control groups that received active treatment. Two independent researchers (AV and AD) extracted summary data, which were verified by a third researcher (JKK). The effect size Hedges' g, 95% CI, and p value were calculated for each target outcome. We applied a random-effects model to all analyses due to the expected heterogeneity between RCTs. We assessed quality using the Risk of Bias 2 tool (dated Aug 22, 2019) and assessed publication bias via the Egger's test, and the Duval and Tweedie trim-and-fill analysis. The study was registered with PROSPERO, CRD42022310762.

We retrieved 12 705 records from electronic databases and 74 records from other sources (ie, reviews and meta-analyses on digital interventions for mental health identified through database searches and their reference lists, reference lists of other studies, trial registrations in PROSPERO, and websites of researchers in the field). Of these, we included 72 RCTs (70 reports) with 21 702 participants (of the 21 048 participants with sex or gender data, 14 208 [67%] were female, 6744 [32%] were male, and 96 [<1%] were other). At post assessment (assessment after completion of intervention), we found significant effects of apps targeting depression (33 comparisons; Hedges' g 0·45 [95% CI 0·30 to 0·60], p≤0·0001, I²=81·30%), anxiety (23 comparisons; 0·35 [0·22 to 0·48], p≤0·0001, I²=74·91%), sleep problems (14 comparisons; 0·71 [0·51 to 0·92], p≤0·0001, I²=76·17%), post-traumatic stress disorder (nine comparisons; 0·15 [0·02 to 0·28], p=0·029, I²=28·65%), eating disorders (four comparisons; 0·50 [0·29 to 0·71], p≤0·0001, I²=50·49%), and body dysmorphic disorder (three comparisons; 0·86 [0·30 to 1·41], p=0·0025, I²=74·90%) compared with inactive control groups. No significant pooled effects were found for smoking (six comparisons), self-injury (six comparisons), suicidal ideation (five comparisons), and alcohol misuse (five comparisons). Effect sizes for obsessive-compulsive disorders (two comparisons) and schizophrenia (one comparison) ranged from 0·10 to 0·96 (-0·12 to 1·51). Risk of bias was moderate to high. Publication bias was found for RCTs targeting depression and anxiety, but not for sleep problems; adjustments reduced the effect sizes for depression from 0·45 to 0·18 (0·02 to 0·34) and anxiety from 0·35 to 0·18 (0·03 to 0·32), with no change for sleep problems.

Although some outcomes showed small to medium effect sizes, these results must be interpreted cautiously given the presence of uncertainty factors, including considerable heterogeneity and moderate study quality. Heterogeneity might result from sample characteristics, assessment methods and periods, dropout rates, intervention and app components, and control conditions, limiting the generalisability of findings. Standalone smartphone apps might be offered for symptoms of depression, anxiety, and sleep problems, if no evidence-based first-line intervention is available.

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