RCT Protocol for 'OverThinking': A Mobile EMI for Reducing Experiential Avoidance

The goal of this trial is to examine whether a mobile app intervention for rumination can modify a maladaptive feature of repetitive negative thinking (RNT) - this is understood by the link between daily RNT and well-being, depressive and anxiety symptoms.

The main questions it aims to answer are:

1. If the intervention can modify the maladaptive feature of repetitive negative thinking - the investigators anticipate the link between daily rumination and maladaptive outcomes (poorer wellbeing, higher depressive/anxious symptoms) will be weaker in the intervention groups.
2. By examining (1) above, to confirm the role played by avoidance in repetitive negative thinking.
3. By splitting the intervention condition into two groups (one receiving concurrent support from a therapist, one not), to evaluate if interventions such as these might be enhanced by therapist support.
4. To examine if the impact of the intervention on depressive and anxious symptoms might be mediated by changes in beliefs regarding emotions (e.g. the valuation of negative emotions).

Researchers will compare across four groups to examine the above effects:

(1) intervention condition (therapist support); (2) intervention condition (no therapist support); (3) Partial intervention (daily sampling and emotion valuation questions); (4) Control group (only daily sampling questions).

Participants will:

* Be requested to participate in a four-week intervention, providing daily assessments of depressive and anxiety symptoms, affect, repetitive negative thinking, and rumination outcomes.
* Use a mobile application during the intervention period, which has been designed by the research team (intervention groups), or provide daily assessment scores only (control groups).
* Be assessed at pre-intervention (all groups), post-intervention (all groups), 1-month follow-up (all groups), and 3-month follow-up (intervention groups only).

The trial aims to examine whether a mobile application-based intervention for experiential avoidance in the context of rumination can modify a maladaptive feature of repetitive negative thinking (RNT) - this is understood by the link between daily RNT and well-being, depressive and anxiety symptoms.

The main questions which the trial aims to answer are as follows:

1. If the intervention can modify the maladaptive feature of repetitive negative thinking - the investigators anticipate the link between daily rumination and maladaptive outcomes (poorer wellbeing, higher depressive/anxious symptoms) will be weaker in the intervention groups.
2. By examining (1) above, to confirm the role played by avoidance in repetitive negative thinking.
3. By splitting the intervention condition into two groups (one receiving concurrent support from a therapist, one not), to evaluate if interventions such as these might be enhanced by therapist support.
4. To examine if the impact of the intervention on depressive and anxious symptoms might be mediated by changes in beliefs regarding emotions (e.g. the valuation of negative emotions).

Researchers will compare across four groups to examine the above effects:

(1) intervention condition (therapist support); (2) intervention condition (no therapist support); (3) Partial intervention (daily sampling and emotion valuation questions); (4) Control group (only daily sampling questions).

The trial comprises of a four-arm, parallel group randomised-controlled trial (RCT). Participation lasts approximately 2 months (including eligibility screening and random allocation to condition (random number generator), a four-week intervention period delivered via the mobile application and supplemented with daily assessments, post-intervention assessments, and 1-month follow-up (wherein the app will remain available for self-directed use without daily sampling), concluding with follow-up assessments and measurement of any engagement with the application during this period.

At the point of 1-month follow-up, participants previously allocated to the control groups will receive access to the application (without the feature of daily sampling) and will be provided with guidance on using the intervention content. While a 3-month follow-up assessment of intervention participants is planned, the 1-month interval allows for control participants to access intervention content without being subject to extensive waitlist delay. Active control groups have been chosen to not artificially inflate comparisons with outcomes in the intervention conditions.

Analysis:

Analysis of changes in outcomes across pre-, post- and follow-up-measures (PTQ, EBQ, PBRS, NBRS, HADS, CAQ, and BEAQ) across all four conditions will be conducted using mixed-design ANOVA.

Additionally for all conditions, multilevel models (daily observations on level 1 nested in participants on level 2) will be used on daily sampling data to assess the links between avoidance and mood and between rumination and mood, and to determine if each of these links is moderated by condition. Participants respond to these items once daily in the evening, in response an in-app reminder alert (the time of the alert can be determined by the participant). All daily sampling items have been provided in the 'Measures' section.

Mixed-design ANCOVA will be used for the two intervention groups to examine if time spent engaging with the application content acts as a covariate in intervention outcomes (PTQ, EBQ, PBRS, NBRS, HADS, CAQ, and BEAQ).

Finally, ongoing development of the application will be assisted using in-app user-feedback data obtained via CORTO implementation (three items with gather a combination of quantitative and qualitative data \[Lukka et al,. 2024\]). This data will be coded deductively using the process outlined by Saldana (2016) and using the four categories identified by Lukka et al. (2024) as high-level guidance ((1) contextual use, (2) interaction-elicited emotional experience, (3) usability, and (4) technical issues.), with more detailed coding examined as subdomains.

Eligibility Criteria:
Inclusion Criteria:

- Self-reporting problems with repetitive negative thinking.

Exclusion Criteria:

* Aged below 18 years at the commencement of the trial.
* Currently in receipt of any form of psychotherapy.
* Currently in receipt of any form of psychiatric medication.

Note: Participants who hold a psychiatric diagnosis will not be excluded from the trial provided they meet the inclusion criterion and do not meet any of the exclusion criteria listed above.