Presentation abstract: Background Depression and anxiety remain the most common form of mental illness in Canada among people 15 years and older. There are numerous barriers to evidence-based treatment options for depression and anxiety, such as clinician availability, accessibility, stigma and cost. Mobile mindfulness interventions hold promise as a way to overcome these barriers and to provide accessible psychological supports. However, few studies on the effectiveness of this in clinical populations exist. The current study examines an innovative mobile mindfulness intervention to individuals waiting for psychological services, in a novel evaluation of the benefits of digital health supports at this critical part of the care journey. Methods Participants include 100 adults (aged 18 to 66, M= 33.1, SD=10.6; 70% female, 29% male, 1% other) waiting for psychological services in the Greater Toronto Area who completed a single-arm clinical trial. Participants completed a set of baseline self-report measures of depression, anxiety, stress, mindfulness, and functional disability. Questionnaires were repeated at weeks 2, 4, 8 and 12. Credibility of the app was assessed at baseline only, and treatment acceptability and usability metrics were assessed at all time points. Participants were provided access to the mobile mindfulness intervention, AmDTx, and were asked to use the app for a minimum of 1 month. User engagement and wellbeing were tracked via the app for 3 months. Multi-level modelling was conducted to examine changes in clinical outcomes. Regression-based analyses evaluated the associations between engagement metrics and clinical outcomes. Results Perceptions of credibility were good (73.2%), suggesting the app was perceived as logical, useful, and recommended. Treatment acceptability ranged from 67.8% to 74.0%. Participants also provided positive feedback regarding ease of use (73.1% to 76.1%), satisfaction with the interface (70.0% to 72.1%), and perceived usefulness (68.3% to 69.0%) on subscales of the mHealth App Usability Questionnaire. At baseline, participants demonstrated clinically significant levels of depression and anxiety severity, and elevated stress and functional disability. All clinical outcomes decreased significantly from baseline to week 12 (bs range from -.45 to -.75; all ps < .05), and there were no significant differences between age and sex. Mindful awareness and acceptance of emotional experiences increased significantly from baseline to week 12 (bs = .14 and .20, respectively; both ps < .01). Engagement metrics were associated with some clinical outcomes, including depression symptom severity and functional disability. Mindfulness outcomes were also associated with engagement, including the number of minutes spent meditating and the total minutes spent on the app. Conclusion Overall, the current study represents an interim analysis of an ongoing investigation of a mobile mindfulness intervention (AmDTx). Early results support the potential benefits of this app for clinical outcomes; however, causal links of benefits to the intervention itself remain to be clarified in future controlled studies. This study highlights the potential for digital interventions to provide valuable mindfulness skill building and additional supports for those waiting for psychological services. CONFIDENTIALITY NOTICE: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. AVIS DE CONFIDENTIALITÉ : Ce message électronique, ainsi que tout fichier qui y est joint, est reserve à l'usage exclusif du destinataire visé et peut contenir des renseignements confidentiels et privilégiés. Toute lecture, utilisation, divulgation ou distribution non autorisée est interdite. Si vous n'êtes pas le destinataire visé, veuillez en aviser l'expéditeur par retour de courriel et détruire toutes les copies du message original.