ZeroOCD: Learn to Overcome Contamination OCD With Your Smartphone

Yale-Brown Obsessive Compulsive Scale (Y-BOCS): Change from baseline in the observer-rated severity of OCD symptoms. This is a 10-item, clinician-rated scale that provides separate subtotals for the severity of obsessions and compulsions. Total scores range from 0 to 40, with higher scores indicating more severe symptoms. The Y-BOCS is also used for the eligibility (mean score > 7).

4-item Obsessive-Compulsive Inventory (OCI-4): Change from baseline in the self-reported OCD symptom severity. This shorter form of the OCI-R consists of 4 Items that quantify the symptom severity related to OCD. Each item is rated on a scale from 0 to 4, with total scores ranging from 0 to 16, with higher scores indicating more severe symptoms.

Padua Inventory (PI) Contamination Fear Subscale: Change from baseline in the self-reported fear of contamination. This is a 10-item subscale that quantifies the severity of contamination-related obsessions, with each item rated on a 5-point Likert scale. A score of 6 or higher on this scale is an inclusion criterion for the study. The PI is also used for the eligibility (mean score > 6).

Patient Health Questionnaire-9 (PHQ-9): Change from baseline in self-reported depressive symptom severity. This is a 9-item measure where each item corresponds to a DSM-5 criterion for major depression. Scores range from 0 to 27, and a score of >20 is an exclusion criterion. The PHQ-9 is also used for the eligibility (severe depressive symptoms: score > 20; suicidality: item 9 score > 2).

Generalized Anxiety Disorder 7-item scale (GAD-7): Change from baseline in self-reported anxiety symptom severity. This is a 7-item measure with scores ranging from 0 to 21. It will also be used at baseline to help determine if contamination fears are due to GAD rather than OCD.

Subjective Units of Distress Scale (SUDS): Measurement of current distress and disgust levels before, during, and after exposure tasks within the ZeroOCD app. This is an ecological momentary assessment (EMA) where participants rate their distress on a visual analog scale from 0 to 10.

World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0): Change from baseline in self-reported general functioning and disability. This is a 36-item measure that evaluates functioning across six major life domains (e.g., cognition, mobility, life activities).

EQ-5D-5L measures change from baseline in self-reported health-related quality of life. This is a 5-item standardized questionnaire that evaluates health status across five domains (e.g., mobility, self-care, pain/discomfort).

Treatment Inventory of Costs in Patients with Psychiatric Disorders (TiC-P): Change from baseline in the utilization of healthcare services and productivity losses. This is a 36-item self-report measure used for the cost-effectiveness analysis.

System Usability Scale (SUS): A global assessment of the subjective usability of the ZeroOCD app, measured post-treatment. This is a 10-item questionnaire with total scores ranging from 0 to 100, where higher scores indicate greater perceived usability.

Client Satisfaction Questionnaire (CSQ): A measure of client satisfaction with the received treatment, assessed post-treatment. This is an 8-item self-report measure with total scores ranging from 8 to 32, where higher scores indicate greater satisfaction.

Realism subscale of the IGroup Presence Questionnaire (IPQ): A measure to assess the perceived realism of the augmented reality (AR) environment, administered post-treatment to the ZeroOCD group. This is a 4-item subscale relevant for AR with each item assessed on a 7-point Likert scale (from -3 to 3).

Negative Effects Questionnaire (NEQ): A measure to evaluate any negative effects of the psychological treatments, assessed at post-treatment and follow-up. This is a 20-item questionnaire where participants report on the occurrence, negative impact, and attributed cause of potential negative events.

To understand the dose-response relationship in treatment effectiveness by analyzing how participants interact with the ZeroOCD app. This involves collecting data automatically from the app for participants in the intervention condition. Data points include the frequency and duration of practice during AR exposure, time spent in each module, number of modules and pages completed, and number of log-ins.

Reasons for discontinuation: to understand why participants stop with the treatment before the end of the treatment

Socio-demographic questionnaire: To gather participant characteristics and demographics at the start of the study. This questionnaire collects information about participants' age, gender, education level, marital status, employment status, and treatment preference. It also gathers information on current or past psychological treatment and medication to confirm eligibility.

Short Health Anxiety Inventory (SHAI): A self-report measure to assess the presence of health anxiety at baseline, which is an exclusion criterion if judged to be the primary driver of contamination fears. This is an 18-item measure rated on a scale from 0 to 3.