Promoting Emotional and Autonomic Control Through Guided Breathing Exercises for Emerging Adults With Autism

Calculated as (1) a time domain measure (RMSSD: Root Mean Square of Successive Differences). Three-lead electrocardiographic data will be captured using the NeXus-10 MKII biofeedback device and Biotrace+ Software (MindMedia B.V., The Netherlands). Disposable, self-adhesive and pre-gelled electrodes (Kendall™ ECG Electrodes Arbo™ H124SG, Covidien, Ireland) will be used without specific skin preparations at a sampling rate of 256 SPS. For the recording of the breathing frequency, an elastic band with stretch-sensitive sensors and a sampling rate of 32 SPS is placed around the waist.

Calculated as (2) a frequency domain measures (HF-HRV). Three-lead electrocardiographic data will be captured using the NeXus-10 MKII biofeedback device and Biotrace+ Software (MindMedia B.V., The Netherlands). Disposable, self-adhesive and pre-gelled electrodes (Kendall™ ECG Electrodes Arbo™ H124SG, Covidien, Ireland) will be used without specific skin preparations at a sampling rate of 256 SPS. For the recording of the breathing frequency, an elastic band with stretch-sensitive sensors and a sampling rate of 32 SPS is placed around the waist.

(1) Symptom Checklist-90 Revised (SCL-90-R): The Dutch version measures eight dimensions: anxiety (ANG), agoraphobia (AGO), depression (DEP), somatization (SOM), cognitive-performance deficits (IN), interpersonal sensitivity and mistrust (SEN), hostility (HOS), and sleep difficulties (SLA). Each item is rated on a 5-point Likert scale from 1 ("not at all") to 5 ("extremely"). The total score ranges from 90 to 450. The total score provides a general measure of psychological distress. Higher scores indicate more symptoms and distress.

The scores on the eight dimensions range for ANG between 10 and 50, for AGO between 7 and 35, for DEP between 16 and 80, for SOM between 12 and 60, for IN between 9 and 45, for SEN between 18 and 90, for HOS between 6 and 30 and for SLA between 3 and 15. Higher scores indicate more symptoms and distress.

(2) Depression Anxiety Stress Scales (DASS-21): The Dutch version of the DASS-21 measures the presence of symptoms of depression, anxiety, and stress. In consists of 21 items and takes about 10 minutes to complete. Each item is rated on a 4-point Likert scale from 0 ("did not apply to me at all") to 3 ("applied to me very much, or most of the time"). The scale yields three subscale scores: Depression, Anxiety, and Stress, each based on 7 items. Subscale scores therefore range from 0 to 21. To calculate the scores, the subscale scores are multiplied by two, resulting in a final range of 0 to 42 per subscale. Higher scores indicate greater symptom severity.

(3) Perceived stress scale (PSS-10): The Dutch version of the PSS measures the degree to which situations in one's life are appraised as stressful, that is, how unpredictable, uncontrollable, and overloaded respondents experience their lives. It consists of 10 items and takes maximum 5 minutes to complete. Each item is rated on a 5-point Likert scale ranging from 0 ("never") to 4 ("very often"). Four items are positively stated and are reverse-scored (item 4,5,7 en 8). Total scores range from 0 to 40, with higher scores indicating higher levels of perceived stress

The investigators will explore how participants experience the guided breathing protocols, including their usability. This aspect will be assessed through a self-report questionnaire, including the registration of perceived stress before and after each sessions, using a Visual Analogue Scale (VAS) ranging from "none" to "a lot".

The investigators will explore how participants experience the guided breathing protocols, including their acceptability. This aspect will be assessed through a self-report questionnaire, including the registration of the overall experience of each session, using a Visual Analogue Scale (VAS) after each session going form "very unpleasant" to "very pleasant".

The investigators will explore how participants experience the guided breathing protocols, including their, safety. This aspect will be assessed though self-report questionnaires, including the registration of adverse events and mild negative reactions.

The investigators will explore how participants experience the guided breathing protocols, including their, safety. This aspect will be assessed though through observations and contact with the investigator during the guided intervention sessions

The investigators will explore how participants experience the guided breathing protocols, including their, safety. This aspect will be assessed though the registration of adverse events and mild negative reactions.

The investigators will explore how participants experience the guided breathing protocols, including their acceptability, safety, usability and adaptability to daily life. These aspects will be assessed through in-depth interviews. The interview guide was developed based on the Theoretical Framework of Acceptability (TFA). This framework allows for a comprehensive exploration of intervention acceptability through seven key constructs (affective attitude, burden, ethicality, intervention coherence, opportunity costs, perceived effectiveness, and self-efficacy).

The investigators will explore how participants experience the guided breathing protocols, including their usability. This aspect will be assessed through a self-report questionnaire, namely: the System Usability Scale (SUS), which will provide insight into the usability of the digitally delivered home-based training. Each item will be scored on a five-point Likert scale ranging from "strongly disagree" to "strongly agree. The item scores are summed to calculate the total SUS score, which ranges from 0 to 100, representing the overall system usability. Overall scores from 0 to 50 indicate "not acceptable," 51 to 70 indicate marginal level of usability, and 71 to 100 indicate "acceptable" levels of usability.