Unguided Internet-based Cognitive Behavioral Therapy (iCBT) is a cost-effective intervention, where users complete structured, evidence-based CBT modules online without therapist involvement. The programs focus on teaching users techniques like identifying and challenging negative thoughts to manage - in this context - Alcohol Use Disorder symptoms.

Guided Internet-Based Cognitive Behavioral Therapy (iCBT) utilizes the structured, online delivery of CBT modules but adds regular, personalized support from a human therapist or trained coach. This human component typically involves checking assignments, providing motivational feedback, and tailoring advice to significantly boost user adherence and clinical outcomes.

The 10-item System Usability Scale will be used to measure subjective usability of internet-based interventions. The items are rated on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). The minimum score is 0 and the maximum score is 100. Higher scores indicate better usability.

The Readiness-to-Change Questionnaire - Treatment Version is a 12-item measure designed to assess the respondent's stated intentions regarding changing their drinking behaviour. It includes three subscales representing different stages of change: (1) Pre-contemplation, (2) Contemplation, and (3) Action. Each subscale consists of four items, and responses are rated on a 5-point Likert Scale ranging from -2 (strongly disagree) to +2 (strongly agree). Total scores can range from -24 to +24. Higher scores on a specific subscale indicate greater alignment with that stage of change.

The Alcohol Use Disorders Identification Test consists of 10 items assessing alcohol consumption, drinking behaviours, and alcohol-related problems. Items 1 to 8 are scored 0, 1, 2, 3 or 4, while items 9 and 10 are scored 0, 2 or 4. The total score can range from 0 to 40, with 0 indicating an abstainer who has never experienced any alcohol-related problems. In the study, only individuals who score ≥8 for men and ≥6 for women will be included, as scores from 1 to 7 for men and 1 to 5 for women suggest low-risk alcohol consumption according to WHO guidelines. Scores of 8 to 15 for men and 6 to 13 for women indicate hazardous or harmful alcohol consumption, while scores above 15 for men and above 13 for women suggest the likelihood of alcohol dependence (moderate-severe alcohol use disorder).

The Drug Use Disorders Identification Test consists of 11 items assessing drug use patterns and drug-related problems (excluding alcohol). Items 1 to 9 are scored 0, 1, 2, 3 or 4, while items 10 and 11 and are scored 0, 2 or 4. The total possible score ranges from 0 to 44, with higher scores reflecting higher drug dependence. A score of 6 for men and 2 for women indicates drug-related problems or harmful drug consumption, while a score of greater than 24 for both sexes suggests probable dependence on one or more drugs.

The EuroQol five-dimensions-five-levels assesses quality of life across five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, with five levels of severity for each (no problems, slight problems, moderate problems, severe problems, or extreme problems). The health state profile is converted into a single index value using the Danish value set (Jensen et al., 2023). In this context, the maximum score is 1.0, while the minimum score is -0.757. Higher scores indicates higher quality of life.

Participants rate their overall health on a vertical visual analogue scale. The scales ranges from 0 to 100. Higher scores indicate greater overall health perception.

The Brief Symptom Inventory 18 is an 18-item questionnaire designed to assess psychological distress. Each item describes a symptom, and respondents rate the extent to which they have been bothered by the symptom over the past week on a 5-point scale, ranging from 0 (not at all) to 4 (extremely). Scores for all items are summarized on the Global Severity Index. The minimum score is 0 and the maximum score is 72. Higher scores indicate higher levels of psychological distress.

The 12-item Buss-Perry Aggression Questionnaire - Short-Form consists of four subscales measuring hostility, anger, and physical and verbal aggression. Each subscale consists of three items, and responses are rated on a 5-point Likert scale ranging from 1 (extremely unlike me) to 5 (extremely like me). The minimum score is 12 and the maximum score is 60. Higher scores indicate higher levels of aggression.

The Negative Effects Questionnaire includes 20 items rated on a 5-point Likert scale ranging from 0 (not at all) to 4 (extremely), distinguishing between negative effects attributed to the intervention and those potentially caused by other factors. The minimum score is 0 and the maximum score is 80. Higher scores indicate a higher burden of negative effects.

Information on highest achieved education, employment, and economy will be retrieved.

Data on inpatient and outpatient Alcohol Use Disorder-related contacts, prior Alcohol Use Disorder treatment, and other comorbidities will be collected.

Data on Alcohol Use Disorder treatment duration and intensity, treatment retention and type of treatment conclusion (i.e., dropout or completion), and prior Alcohol Use Disorder treatment will be retrieved.

Data on Alcohol Use Disorder treatment duration and intensity, treatment retention and type of treatment conclusion (i.e., dropout or completion), and prior Alcohol Use Disorder treatment will be retrieved.

Data on prescription of pharmacological treatment targeting Alcohol Use Disorder (e.g. disulfiram, naltrexone) and number of released receipts will be retrieved.

Data on inpatient and outpatient Alcohol Use Disorder-related contacts, prior Alcohol Use Disorder treatment, and other comorbidities will be collected.

Data on the date and primary cause of death, including both internal and external causes (accident, suicide, or murder), will be retrieved.