BackgroundAlthough text messaging has the potential to be the core intervention modality, it is often used as an adjunct only. To improve health and alleviate the distress related to insomnia, pain, and dysregulated eating of people living in urban areas, text messaging–based mindfulness-based interventions were designed and evaluated in 3 randomized controlled trials.ObjectiveThis study investigated the effectiveness and mediating mechanisms of text messaging–based mindfulness-based interventions for people with distress related to insomnia, pain, or dysregulated eating.MethodsIn these trials, 333, 235, and 351 participants were recruited online and randomized to intervention and wait-list control conditions for insomnia, pain, and dysregulated eating, respectively. Participants experienced 21 days of intervention through WhatsApp Messenger. Participants completed pre-, post-, 1-month follow-up, and 3-month follow-up self-report questionnaires online. The retention rates at postmeasurements were 83.2% (139/167), 77.1% (91/118), and 72.9% (129/177) for intervention groups of insomnia, pain, and dysregulated eating, respectively. Participants’ queries were answered by a study technician. Primary outcomes included insomnia severity, presleep arousal, pain intensity, pain acceptance, and eating behaviors. Secondary outcomes included mindfulness, depression, anxiety, mental well-being, and functional impairments. Mindfulness, dysfunctional beliefs and attitudes about sleep, pain catastrophizing, and reactivity to food cues were hypothesized to mediate the relationship between the intervention and outcomes.ResultsFor all 3 studies, the intervention groups showed significant improvement on most outcomes at 1-month follow-up compared to their respective wait-list control groups; some primary outcomes (eg, insomnia, pain, dysregulated eating indicators) and secondary outcomes (eg, depression, anxiety symptoms) were sustained at 3-month follow-up. Medium-to-large effect sizes were found at postassessments in most outcomes in all studies. In the intervention for insomnia, mediation analyses showed that dysfunctional beliefs and attitudes about sleep mediated the effect of the intervention on all primary outcomes and most secondary outcomes at both 1-month and 3-month follow-ups, whereas mindfulness mediated the intervention effect on presleep arousal at 1-month and 3-month follow-ups. In the intervention for pain, pain catastrophizing mediated the effect of intervention on pain intensity and functioning at both 1-month and 3-month follow-ups, whereas mindfulness only mediated the effect of intervention on anxiety and depressive symptoms. In the intervention for dysregulated eating, power of food mediated the effect of intervention on both uncontrolled and emotional eating at both 1-month and 3-month follow-ups and mindfulness was found to mediate the effect on depressive symptoms at both 1-month and 3-month follow-ups.ConclusionsThese 3 studies converged and provided empirical evidence that mindfulness-based interventions delivered through text messaging are effective in improving distress related to sleep, pain, and dysregulated eating. Text messaging has the potential to be a core intervention modality to improve various common health outcomes for people living a fast-paced lifestyle.Trial RegistrationClinical Research and Biostatistics Clinical Trials Registry CUHK_CCRB00559; https://tinyurl.com/24rkwarz