Despite considerable, replicated evidence of the efficacy and effectiveness of cognitive behavioural therapy, there is an insufficient number of professionals (e.g., psychologists, psychiatrists) in North America to provide evidence-based psychotherapy to all who need it. Seminal work from Statistics Canada has emphasized the need for greater access to psychotherapy in Canada. Moreover, in light of the COVID-19 pandemic, there is a greater need for resources that are scalable to help a large portion of the public to manage anxiety and attendant psychological distress. One promising avenue to increase the availability of evidence-based mental healthcare relies on technological developments, such as smartphone-enabled apps, to disseminate principles derived from existing evidence-based psychotherapies. The internet and smartphones provide a novel format to provide information and relevant skills to a large number of users. Recent research indicates that internet-based variants of cognitive behavioural therapy may be efficacious treatments for anxiety and depressive disorders among other conditions. Critically, internet-based treatments are scalable; resources can be provided to many people instantaneously to help them in crises, such as the COVID-19 pandemic. Further study is needed to identify who may benefit from internet-based treatment or require psychotherapy in a more traditional format. For example, whereas mental health professionals receive extensive training in assessment and case formulation to adapt treatments to individuals, internet-based resources are fixed. However, their fixed nature allows internet-based resources to offer a range of tools for users to try in a process of finding those that benefit them in particular situations. Moreover, the ability to access resources on demand presents a unique benefit of internet-based treatments that may support goals of traditional psychotherapy formats to generalize skills into individuals' daily lives. Anxiety disorders are also frequently comorbid with myriad other psychological and psychiatric conditions. Existing treatments for other conditions are often complicated by the presence of a comorbid anxiety disorder, which may be associated with poorer prognosis. Whereas traditional psychotherapy formats consider how to organize treatment for multiple comorbid conditions, internet- and smartphone-enabled resources may help individuals manage concurrent anxiety to support traditional treatment in addressing comorbid conditions. For example, anxiety disorders are often comorbid with substance use disorders; internet- and smartphone-based resources for anxiety disorders may, therefore, supplement existing treatments for substance use disorders for some individuals.

In recent years, there has been a proliferation of smartphone-based apps advertised to help users' mental health and wellness. While many of these apps may use principles of evidence-based treatments, the efficacy, effectiveness, or clinical utility of most apps has not been empirically supported. Overall, internet-based mental health resources may provide useful help to people for whom traditional psychotherapy is not yet available or to augment existing treatment such as through helping to generalize therapeutic skills into one's daily life. However, further research is needed to understand for whom and in what contexts internet- and smartphone-enabled resources are helpful. The present study will examine the utility of one such smartphone enabled app, MindShift, developed by Anxiety Canada in consultation with Canadian and American experts in evidence-based psychotherapy for anxiety disorders. Specifically, the main aim of the present study is to evaluate the effectiveness of the MindShift app to help users manage anxiety and related psychological distress as compared to anxiety and distress prior to app use. Two secondary, exploratory aims of the present study are to examine possible moderators that indicate for whom or in what contexts use of the MindShift app is particularly helpful. Specifically, the research team will examine person-specific and contextual moderators of change over time. For example, the person-specific moderator of baseline anxiety severity may demonstrate a non-linear association with change in anxiety severity over time, which would indicate that the smartphone-based resource is more helpful for individuals in a given range of baseline anxiety severity (e.g., low to moderate) while other treatment formats should be considered for individuals with severe baseline anxiety. Similarly, differences in the rate of anxiety symptom change over time will examine whether use of the app is associated with greater reductions in anxiety and distress when used alone or as an adjunct to traditional psychotherapy or pharmacotherapy. Finally, by examining comorbid conditions and concurrent treatments as moderators of change in anxiety severity over time, the present study will provide some of the first indications of whether use of the MindShift smartphone app to manage anxiety supports existing treatments for conditions frequently comorbid with anxiety disorders.

Adult participants 18 years of age and older will be recruited from Canada and the United States of America using a variety of online platforms and list serves. Following informed consent, participants will complete baseline assessment of anxiety symptom severity, depressive symptom severity, daily functional impairment, quality of life, alcohol use, use of illicit psychoactive substances, stress associated with the COVID-19 pandemic, and demographic information. Following baseline assessment, participants will be instructed in downloading the MindShift app to their personal mobile phone running either iOS or Android OS software. Participants will then use the MindShift app as they choose for the 16-week duration of the study. Finally, participants will be asked to complete follow-up assessments 2, 4, 8, 12, and 16 weeks following baseline assessment. Follow-up assessments will assess anxiety symptom severity, depressive symptom severity, functional impairment, and quality of life satisfaction on the same measures administered at baseline.