Is internet-delivered treatment specifically for symptoms of generalised anxiety disorder as effective as internet-delivered treatment for symptoms of both anxiety and depression, and are self-guided versions of these as effective as therapist-guided versions?

INTERVENTION: In this trial Australian adults with symptoms of generalised anxiety disorder will be randomly allocated to one of four groups. Two of the four groups will receive access to an 8 week internet‐delivered treatment course specifically for generalised anxiety disorder (disorder‐specific treatment course). The other two groups will receive access to an 8 week internet‐delivered treatment course for symptoms of anxiety and depression (trans‐diagnostic treatment course). Over the 8 weeks, all participants will be directed to read 5 online lessons about management of symptoms. One lesson will be completed every 7 to 14 days. Each lesson will take about 15 minutes to read. Participants will also have access to summaries and homework assignments for each lesson, and will read stories about people with similar symptoms, taking a further 20 minutes per week. The four groups are: Group 1: Self‐guided ‐ disorder‐specific course. Participants in this group will complete the disorder‐specific generalised anxiety disorder treatment course in a self‐guided format, that is, without support from a therapist. Group 2: Self‐guided ‐ trans‐diagnostic. Participants in this group will complete the trans‐diagnostic treatment course in a self‐guided format, that is, without support from a therapist. Group 3: Guided ‐ disorder‐specific. Participants in this group will complete the disorder‐specific generalised anxiety disorder treatment course in a guided format, that is, with weekly telephone or email support from a therapist. Group 4: Guided ‐ trans‐diagnostic. Participants in this group will complete the trans‐diagnostic treatment course in a guided format, that is, with weekly telephone or email support from a therapist. Participants in all groups will also receive twice weekly automatic emails providing reminders about the course and encouragement to continue. Study questionnaires will be administered at pre‐treatment, post‐treatment, and at 6, 12, and 24 months post‐treatment. These will take about 20‐30 minutes to complete. Participants will also complete brief measures of mood and anxiety before each lesson. The treatment materials include cognitive behavioural treatment (CBT) skills. CONDITION: Generalised anxiety disorder PRIMARY OUTCOME: Symptoms and severity of anxiety are measured by the Generalised Anxiety Disorder 7 Item Scale (GAD‐7) SECONDARY OUTCOME: Disability is measured by the Sheehan Disability Scales (SDS) Health service use will be measured by the Service Use Questionnaire Health status is measured by the European Quality of Life‐5 Dimensions‐ 5 Level (EQ‐5D‐5L) Positive adaptive behaviours are measured by the Things You Do Questionnaire (TYD) Psychological distress is measured with the Kessler‐10 item (K‐10) Symptoms and severity of low mood/depression are measured by the Patient Health Questionnaire‐9 (PHQ‐9) Symptoms and severity of panic disorder are measured by the Panic Disorder Severity Rating Scale ‐ Self Report (PDSS‐SR) Symptoms and severity of social anxiety are measured by the MINI‐Social Phobia Inventory (MINI‐SPIN) Working alliance is measured by the Working Alliance Inventory (WAI) INCLUSION CRITERIA: 1. Self‐identifying as having difficulties with symptoms of generalised anxiety disorder. 2. Elevated symptoms of generalised anxiety disorder as indicated by a score of 5 or more on the GAD‐7, indicating at least mild symptoms. 3. No current participation in cognitive behavioural treatment for generalised anxiety disorder. 4. No change in medications in the period 1 month prior to this study. 5. Access to the Internet and a printer. 6. 18 years to 64 years old. 7. Resident of Australia. 8. Prepared to provide name, phone number and address, and to provide the name and address of a local general practitioner 9. Prepared to provide written informed consent.