Study Protocol for a Feasibility Study of a Novel ACT-based eHealth Psychoeducational Intervention for Students With Mental Distress

Acceptance Checklist for Clinical Effectiveness Pilot Trials (ACCEPT)

Depression Anxiety Stress Scales (short-form DASS-21). This is the short version of this measure and is a general psychological distress measure with good construct validity (confirmatory factor analysis of 0.94). It has good internal reliability as measured through Cronbach's alpha coefficients, which are 0.88 for depression, 0.82 for anxiety, 0.90 for stress and 0.93 for the total scale (Henry & Crawford, 2005).

Social connectedness (adapted from Russell's (1996) UCLA Loneliness Scale (Kok et al., 2013). This includes two questions; (1) "During these social interactions, I felt 'in tune' with the person/s around me", and (2) "During these social interactions, I felt close to the person/s." Responses are made on a 7-point scale (1 = not at all true, 7 = very true). The Cronbach's alpha coefficients for these two items ranged from .80 to .98 (M = .94, SD = .03) (Kok et al., 2013).

EuroQol five dimensions (EQ5D). The EQ5D is a measure for health-related quality of life (HRQOL) statues. Within it, there are five components which assess mobility, self-care, usual activities, pain and discomfort, as well as anxiety. It also has a visual analogue scale (VAS) for measuring current health status. Scores for these will be calculated for each of these five subsections as well as including the VIS and total EQ5D score of all five subsections. The EQD5 correlates well with other health related questionnaires such as the SF-36 (r = 0.61, p<0.0001) and PDQ-39 (r = -0.75, p<0.0001) (Schrag, Selai, Jahanshahi, & Quinn, 2000).

Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) (Tennant et al., 2007). Is a measure of mental well-being with a focus on positive aspects of mental health. It has good internal consistency with a Cronbach's alpha coefficient of 0.89 (student sample) and 0.91 (general population sample).

Heart rate variability (HRV). This measures the beat-to-beat variation of the R-R intervals of the electrocardiogram recording and is controlled via the sympathetic and parasympathetic components of the autonomic nervous system (ANS). This is a commonly indexed measure of vagal function and important mediator of health and wellbeing associated with emotion regulation and longevity (Kemp, Arias, et al., 2017) . Measurement of the HRV to assess autonomic changes can be performed using a sensitive and non-invasive technique through an electrocardiogram.

Mindfulness Attention Awareness Scale (MAAS). This is a 15-item scale and is used to measure participant's awareness of moment to moment experiences. This mindful self-awareness can be improved through practicing mindfulness. Also, the absence of this skill correlates with decreased self-awareness (Brown & Ryan, 2003). The scale is rated from 1 (almost always) to 6 (almost never) and are then averaged. The internal validity of the MAAS is high where a Cronbach's alpha coefficient of 0.83 has been reported (Frewen, Evans, Maraj, Dozois, & Partridge, 2008).

Acceptance and Action Questionnaire- second version (AAQ-II). This is a 10 item scale, developed by (Bond et al., 2011) to measure psychological flexibility which involves the ability to accept and be open to difficult thoughts and feelings as well as engage in valued behaviour in the presence of the difficult thoughts and feelings. Higher scores indicate higher psychological flexibility, and the measure has good construct validity with a Cronbach's alpha coefficient of 0.84 (Bond et al., 2011).