The present study will use a randomized controlled design to investigate group differences between university students with self-reported stress (comparison group), ADHD, or a history of nonsuicidal self-injury (NSSI) in response to a four-week mindfulness instruction program across conditions (formal mindfulness program, informal mindfulness program, inactive control) in terms of the intervention's acceptability and effectiveness.

As post-secondary students report increasing levels of stress and difficulty coping with the challenges of university, student services have had to consider alternative approaches to meet the demand for student support. Thus, there has been a move towards extending support beyond traditional mental health services to include the teaching of resilience-building strategies. These resilience-building activities use pedagogical principles and are commonly instructional programs offered to groups of students. These programs often use mindfulness (i.e., purposeful attention to the present moment with nonjudgmental acceptance) as a foundation due to substantial evidence of the benefits of mindfulness in university students. However, subgroups within the university student population may respond differently to standard mindfulness instruction.

Indeed, emerging evidence suggests that mindfulness instruction may be experienced in unique ways by certain vulnerable populations, such as those with a history of non-suicidal self-injury (NSSI; self-injury without lethal intent) or attention-deficit/hyperactivity disorder (ADHD; neurodevelopmental disorder characterized by developmentally atypical levels of inattention and/or hyperactivity-impulsivity). Students with a history of engaging in NSSI comprise 10-39% of university students, while students with ADHD comprise 2-8% of university students. These subgroups of students tend to exhibit a vulnerability to university stressors and stand to incur important benefits from resilience-building strategies that are tailored to their needs.

However, students with history of NSSI or ADHD are predisposed to find standard mindfulness instruction challenging and/or inaccessible. Standard mindfulness instruction generally consists of a combination of formal and informal practice. Formal practices can be conceptualized as structured, sustained attentional guided activities in which mindfulness is practiced within an allotted period of time (e.g., sitting meditation, body scan), whereas informal practices are brief and unstructured, and focus on the experience of one's senses during routine activities (e.g., becoming aware of the feeling of water on one's hands while washing them). Formal practice often requires sustained attention on one's inner experience (i.e., thoughts and emotions) and bodily sensations. Existing difficulties with emotion regulation, self-criticism, and a potentially complex relationship with their body may render this common component of formal mindfulness practice challenging for students with a history of NSSI. For students with ADHD, the elevated level of attentional demand required for formal mindfulness practice may be particularly challenging (e.g., ADHD). Indeed, individuals with ADHD tend to report elevated attrition rates from mindfulness-based programs. If standard mindfulness programming is not properly adapted to individual differences, this may limit its accessibility to university students with a history of NSSI or ADHD.

Promising emerging evidence from our team finds that adolescents, who have difficulties with sustained attention, prefer informal mindfulness practice over formal practice. Specifically, students found the informal practices more accessible (more likely to use in future) than formal practices. This study is an important precursor to the proposed study, given that it provides reason to believe that students with ADHD, who also experience attention difficulties, might similarly find informal mindfulness more accessible. Similarly, a recent study by our team found that university students with a history of NSSI found informal mindfulness practice to be more acceptable than formal practice. Consistent with these exciting early results from our team, in a recent systematic review examining the unique benefits of informal mindfulness, it was concluded that informal practices may be more accessible and acceptable among those already experiencing difficulties with attention or emotion regulation. The need for additional studies exploring the potentially differential effectiveness of formal and informal mindfulness instruction among groups with unique intrapersonal needs was highlighted.

To investigate whether the response to and associated benefit of formal or informal mindfulness instruction differs between students with a history of NSSI or ADHD, the proposed study will use a randomized controlled design to investigate group differences in both the immediate response to, and long-term benefits of, formal versus informal mindfulness instruction. Specifically, the study will assess (1) satisfaction with each mindfulness instruction type quantitatively (through surveys) and qualitatively (through semi-structured interviews), (2) changes in mental health/well-being and educational outcomes over time, across groups (i.e., NSSI, ADHD, comparison) and conditions (i.e., formal, informal), and (3) whether the impact of the instruction (i.e., formal, informal, control) on these outcomes occurs as a function of changes in specific facets of mindfulness.

Inclusion Criteria:

• Current student at McGill University or Concordia University
• 18-29 years old
• Either self-reported stress or self-reported ADHD or a self-reported history of engaging in NSSI on at least 5 separate days in the last year

Exclusion Criteria:

• Having a history of NSSI that does not fulfill the recency/frequency requirement

Following the publication of findings, de-identified data will be uploaded to a public online repository (e.g., the McGill University Dataverse, the Open Science Framework [OSF]).