CBM in the Context of Exposure for Acrophobia

Acrophobia-related interpretational processing biases will be measured using a modified version of the Encoding Recognition Task (ERT, Salemink & van den Hout, 2010). Bias scores of the Encoding Recognition Task can range from -4 to +4, with lower scores indicating a more negative interpretation bias.

The primary outcome is change in bias score from baseline to post-training.

Acrophobia-related interpretational processing biases will be measured using a modified version of the Encoding Recognition Task (ERT, Salemink & van den Hout, 2010). Bias scores of the Encoding Recognition Task can range from -4 to +4, with lower indicating a more negative interpretation bias.

The Heights Interpretation Questionnaire (HIQ; Steinman & Teachman, 2011) asks participants to rate the likelihood of eight negative interpretations for two height-related, ambiguous scenarios. Scores can range from 16 to 80, with higher scores indicating a worse outcome.

Modified version of the Scrambled Sentences Task (Wenzlaff & Bates, 1998), including 20 height-related items that can be unscrambled into positive or negative statements.

The Danger/ Anxiety Expectancy Scale (DES/AES; Gursky & Reiss, 1987) asks participants to rate the likelihood of potential harmful events passing through their mind and the likelihood to experience anxiety symptoms if confronted with heights. Scores can range from 15 to 75, with higher scores indicating a worse outcome.

The Acrophobia Questionnaire (AQ; Cohen, 1977) asks participants to rate their anxiety and avoidance behavior for 20 common height-related situations. Scores can range from 0 to 160, with higher scores indicating a worse outcome.

With the Behavioral Approach Task (BAT), participants' behavioral approach tendencies to height-relevant situations will be assessed by instructing participants to go as high as possible at the emergency staircase at the therapy center and asking participants to rate their subjective fear with the Subjective Units of Distress Scale (SUDS; Wolpe 1973). Scores can range from 0 to 100, with higher scores indicating greater fear.

Via salivary samples, patients' endogenous levels of estradiol and progesterone will be assessed.

Adverse events during the study will be assessed with an adapted version of the Negative Effects Questionnaire, which is a 20-item questionnaire designed to assess potential negative effects of psychological interventions (Rozental et al., 2019), in this context also including the CBM training. Scores can range from 0 to 80, with higher scores indicating more negative effects.

We will use a feedback questionnaire containing both rating scales and open questions to assess patients' feedback about the study and interventions completed.

Scores can range from 21 to 189, with higher scores indicating a more positive feedback.

Symptoms of depression, stress and anxiety will be assessed using the Depression Anxiety Stress Scale-21 (Lovibond & Lovibond, 1995) which consists of seven symptom-related items per subscale. Participants are asked to rate the strength of each symptom in the past week. Scores can range from 0 to 63, with overall higher values indicate more severe symptoms.

We will use the High Place Phenomenon Index (HPPI; Hames et al., 2012; German version: Teismann et al., 2020) to assess how often participants experienced the "high place phenomenon". This phenomenon involves the sudden urge to jump down when being in a high place and thus may be relevant in the context of acrophobia. The index consists of three items about three different height-related situations, and patients have to indicate whether they experienced the high place phenomenon in each situation using a 6-point Likert scale. Scores can range from 0 to 15, with higher scores indicating more frequent experiences of the high place phenomenon.