The efficacy of smartphone-based mental health interventions for depressive symptoms: a meta-analysis of randomized controlled trials. Firth J, Torous J, Nicholas J, Carney R, Pratap A, Rosenbaum S, et al. World Psychiatry. 16(3):287–298. (2017 Oct). PMID: 28941113. doi: 10.1002/wps.20472