esTOCma, an App Used by Teachers: an RCT

Score change in the knowledge and the attitudes towards obsessive-compulsive disorder measured by the OCD Knowledge Stigma Assessment Scale (OKSAS). It is a self-report ad hoc questionnaire with 24 items and a response scale ranging from 1 "Completely disagree" to 5 "Completely agree". The total score is the sum of the items and higher score indicate more knowledge about the disorder.

Score change in stigma will be measured, in association with a vignette, by two questionnaires:

• Attribution Questionnaire (AQ-9; Corrigan et al., 2015; Spanish version: Muñoz et al., 2015) is a self-report measure for social stigma. It has a Likert scale ranging from 1 = "Not at all" to 9 = "Very much". Investigators will not use the items corresponding to Coercion, Pity and Avoidance. The higher the score (total and per item), the higher the stigma.
• OCD Stigma Measure (OSM; Ponzini et al., 2023) is a self-report measure composed by 16 items that assess OCD-related stereotypes. 11 items will be used in this study. A total score (sum of all the items) is interpreted.

There will be two vignettes that will be randomly assigned. Both portray a student with OCD but one focuses on the contamination content, and the other on the aggression content.

Score change in desired social distance will be measured by Reported and Intended Behaviour Scale (RIBS; Evans-Lacko et al., 2011; Spanish version: Sayols-Villanueva et al., 2015). It is a self-report measure with 8 items and it inquires about reported and intended behaviour among four different contexts: (1) living with, (2) working with, (3) living nearby and (4) continuing a relationship with someone with a mental health problem. Investigators will use the 4 items corresponding to intended behaviour subscale. Likert scale from 1 "Agree strongly" to 5 " Disagree strongly" and an additional "Don't know" response option. The total score is calculated by adding together the response values, and "Don't know" is coded as a neutral value (i.e. 3).

This questionnaire will be used in association with a vignette.

Score change in confidence when addressing students with OCD will be measured using items adapted and translated from previous studies (Jorm et al., 2010; Kutcher et al., 2016; Whitley & Gooderham, 2016). Three dimensions are evaluated separately:

Confidence in interacting, composed of three items with a Likert scale ranging from 1 "Completely disagree" to 5 "Completely agree". The total score will be obtained by summing the item responses.

Confidence in helping, assessed with a single item ("To what extent do you feel capable of helping a student like N?") rated on a 5-point scale ranging from 1 "Slightly/Not at all confident" to 5 "Extremely/Very confident".

Academic confidence, measured with two items rated on a 4-point Likert scale ranging from 1 ("Not at all capable/ Lower academic level") to 4 ("Very capable/Highest academic level"). A total score will be computed by summing both items.

Score change in OCD symptoms will be measured by Obsessive-Compulsive Inventory - Revised. The reduced 4-item version (OCI-4; Abramovich et al., 2021) that assesses four dimensions of OCD (washing, checking, ordering, obsessing) will be used. It has a 5-point Likert scale ranging from 0 "Not at all" to 4 "Very much". The items will be added.