CBT will be used as the chosen approach for ADs. The main components will be psychoeducation and to help patients to challenge and change unhelpful cognitive distortions (e.g., thoughts, beliefs, and attitudes) and behaviors (e.g., avoidance), develop emotion regulation strategies (e.g., cognitive reappraisal), and learn coping strategies that target problem-solving. The practice is developed in several sessions that usually last between 10 and 20 sessions. Specifically, the exposure component will be considered as the first-line treatment. During the exposure component, patients will confront themselves over a long period of time, repetitively, with a feared stimulus until distress has decreased significantly by the exposure. In this condition participants will receive CBT treatment and be exposed to in vivo situations with the support of SYMPTOMS-JIT.

The AQ evaluates severity of anxiety and avoidance related to different situations that have to do with heights. It consists of 40 items divided into two subscales. On the one hand, there is an anxiety subscale where it is necessary to indicate the degree of anxiety, tension, or discomfort caused in the situations described, responding on a 0 to 6 point Likert-type scale ("no anxiety, calm and relaxed" - "extremely anxious"); and on the other hand, there is an avoidance subscale, where the response is coded on a 0 to 2 point Likert-type scale ("I would not try to avoid it" - "I would not bear it under any circumstances")

The CLQ consists of descriptions of 26 claustrophobic situations. Participants are asked about the degree to which they would feel anxious in these situations according to a 5-alternative Likert-type scale, where (0) is "not at all anxious" and (4) is "extremely anxious." The CLQ consists of two subscales: restriction of movement, ranging from items 1 to 12, and suffocation, ranging from items 13 to 26.

This is a list of 30 situations related to flying that can cause discomfort or anxiety, divided into three subscales: in-flight situations, pre-flight situations, and vicarious situations. The items (each representing a situation) are rated on Likert scales from 1 (minimal discomfort) to 10 (maximum discomfort), and therefore the score ranges from 30 to 300.

The ASI is a scale composed of 16 items specifying a possible negative consequence to anxiety: additional anxiety or fear, illness, embarrassment and loss of control. The patient is required to rate each item in a 5-point scale, ranging from 0 (very little) to 4 (very much). The ASI has adequate test/retest reliability.

The FQ is a 15-item questionnaire that yields four scores: main phobia, global phobia, total phobia and anxiety-depression; the total phobia score is composed of agoraphobia, social and blood-injury subgroups. It is reliable and valid.

The SIAS assesses fears of general social interaction. It comprises 20 items, rated on a 5-point Likert scale, from 0 (not at all characteristic of me) to 4 (extremely characteristic of me). Internal consistency and test-retest reliability is high.

The FNE is a 30-item true-false inventory measuring anticipation of and distress about being negatively evaluated by others.

The SAD is a 28-item true-false questionnaire measuring subjective distress experienced in social situations and avoidance of such situations.

The PDSS-SR is a self-report that consists of seven items rating frequency of panic attacks on a 5-point scale from 0 to 4, being the total score 28. It has good test-retest reliability and is sensitive to change with treatment.

This instrument measures the types of altered responses (motor (to places, means of transportation, and situations), subjective psychophysiological, and cognitive) of the patient, alone and in company, to the most common stimulus situations, as well as the variability of altered responses. Among the proposed items, patients must also indicate the symptoms that cause them the most difficulties in daily life.

The ODSIS is a five-item instrument designed to measure severity and impairment of depressive symptoms. Items are coded from 0 to 4 and are summed to obtain one total score.

The OASIS is a five-item continuous measure of anxiety-related severity and impairment. Items are coded from 0 to 4 and are summed to obtain one total score. The OASIS have shown high internal consistency, excellent test-retest reliability, and convergent and discriminant validity in clinical and non-clinical samples (i.e., Norman et al., 2006)

Behavioral Avoidance Tests (BATs) are fundamental tools in the assessment and treatment of specific anxiety disorders, such as claustrophobia, acrophobia, panic disorder, and social anxiety. For claustrophobia, a BAT may involve progressively entering confined spaces, such as an elevator or a windowless room, while recording their anxiety level and avoidance behavior. For acrophobia, a BAT could involve gradually climbing to elevated locations, such as stairs or balconies, allowing observation of how they tolerate exposure to height. For panic disorder, interoceptive BATs are used, in which feared physical sensations (such as hyperventilating or spinning in a chair) are induced to assess the patient's reaction to bodily symptoms associated with panic. On the other hand, in social anxiety, a common task in a BAT is to ask the patient to give a speech in front of a small audience or a camera, thereby assessing their level of discomfort, physiological arousal, and avoidance behaviors.

The SF-12 is a self-report that measures the impact of health on everyday life. It comprises 12 items and it is a valid and reliable measure. The internal consistency is great.

It is a 10-item self-report that assesses various aspects of quality of life. These dimensions are rated on a 10-point Likert scale, ranging from 1 (poor) to 10 (excellent). The dimensions include physical well-being, psychological/emotional well-being, self-care and independent functioning, occupational functioning, interpersonal functioning, social-emotional support, community and services support, personal fulfillment, spiritual fulfillment, and overall perception of quality of life. The total score is calculated as the average of all items and ranges from 1 to 10, with scores between 1 and 4.5 indicating a perception of quality of life below average, scores between 4.6 and 8.1 indicating an average perception, and scores between 8.2 and 10 indicating a perception above average. Test-retest reliability (0.89) and internal consistency (α = 0.89) are strong; discriminant validity is demonstrated in a sample of patients with mental illness.

This scale is intended to evaluate the patient's degree of progress over their initial state. The patient rates the items on a scale of 1 (much worse) to 7 (much better).

These two scales consist of six items each. Participants rate these items on a scale from 0 (strongly disagree) to 10 (strongly agree). Their aim is to evaluate the treatment's ability to meet the patients' expectations, its perceived logic, its potential for treating other psychological issues, its usefulness for the patient, the likelihood of recommending it to others and its aversion. The Expectation of Treatment Scale is completed after the description of the intervention, before receiving any treatment and the Satisfaction with the Treatment Scale is completed after it is finished, assessing the patient´s satisfaction with the intervention.

A semi-structured interview developed ad-hoc based on the Expectation and Satisfaction Scale (adapted from Borkovec & Nau) following the principles specified in the CQR guidelines (Hill et al., 2005). This included different open-ended questions that assess satisfaction using the Exposure Therapy App; why they would recommend it to other people with ADs; utility; intrusiveness due to aspects of threat to confidentiality when using this technology; aspects of the tool that make it easier and/or more difficult to use.

The Preference Questionnaire: Traditional In-Live Exposure vs. SYMPTOMS-JIT Exposure is a specially designed instrument to compare the acceptance of two exposure treatment modalities in people with anxiety disorders: one guided by a therapist in real-life settings and the other assisted by a mobile app that allows for autonomous task completion. Through ten items, the questionnaire assesses the patient's willingness to repeat each type of treatment, their preference, perceptions of efficacy, usefulness, logic, aversiveness, and recommendation to others, combining rating scales and multiple-choice options to obtain useful information in clinical or research contexts.

This scale is one of the most popular methods for assessing the usability of ICT applications. The concept of usability describes how simple it is for the users to use a technological tool to accomplish a certain task in a given situation. They must indicate how much they agree or disagree with the 10 items using a 5-point Likert scale, 1 being strongly disagree and 5 being strongly agree).

uMARS consists of 20 items assessing objective and subjective app quality, rated on a 5-point Likert scale ranging from 1 ("poor") to 5 ("excellent"). In addition, items 13-16 include the additional option of "not applicable." The objective quality score is calculated as the mean of the scores of 4 dimensions: engagement (items 1-5), functionality (items 6-9), esthetics (items 10-12), and information (items 13-16). A subjective quality score is obtained as the mean of 4 subjective items (17-20). The final uMARS subscale includes 6 items, designed to assess the perceived impact of the app on the user's awareness, knowledge, attitudes, intention to change, helpseeking, and the probability of changing the target health behavior, also rated on a 5-point Likert scale ranging from 1 ("strongly disagree") to 5 ("strongly agree").