Mobile phone-based mental health interventions have gained popularity as a potential solution to the cost and access issues of traditional mental health care. A new study analyzed previous research on such interventions, including 145 studies involving 48,000 participants, to determine whether they benefit users as designed. Overall, the study found modest positive results for certain conditions – such as anxiety and depression – but little evidence that mobile-phone based interventions are as effective or more effective than traditional care. More rigorous studies, including a full exploration of potential negative outcomes, are necessary to understand the impact of these interventions. To learn more, see the study in PLOS Digital Health.