Clients in the Extended Contact condition will be asked at the 6 week mark if they like they can extend their treatment and receive up to 12 weeks of support. They will be informed that this may be helpful if they feel they have fallen behind in reviewing of the materials, if they would like to receive support while they work on supplementary resources or if they would like extended support while they work on core lessons. If they would like additional support, participants will answer questions presented on the website about their desire for this additional support what they would like to focus on during this time. Those clients who indicate that they would like this extended support will automatically have their therapists check-in with them for up to 12 weeks. Those that do not request the additional support will end treatment as planned at the end of 8 weeks.

In the standard condition, clients will receive 8 weeks of therapist support. They will not be given the option to extend their treatment and support to 12 weeks. The booster course will not be offered in this condition.

Clients in the Extended Contact condition will receive an email at the 6 week mark letting them know that they if they like they can extend their treatment and receive up to 12 weeks of support. At week 6, clients will answer questions on the website about whether they would like this additional support or not and what they would like to focus on during this time. Clients who indicate they would like this extended support will automatically have their therapists check-in with them for up to 12 weeks.

They will also be told that at 16 weeks they will have access to a booster session (online materials that go over core skills such as thought challenging, deep breathing, behavioural activation, and graded exposure). At 16 weeks, they will be sent an email reminder to log in for the booster course. The therapist will send a supportive email to the client offering to assist with any challenges the client reports in the check-in questionnaire by email or phone call over the next 2 weeks.

All clients will receive the Wellbeing Course developed at Macquarie University, Australia. The Wellbeing Course is a transdiagnostic Internet-delivered cognitive behaviour intervention targeting symptoms of depressive and anxiety disorders. It comprises 5 online lessons targeting: 1) symptom identification and the cognitive behavioural model; 2) thought monitoring and challenging; 3) de-arousal strategies and pleasant activity scheduling; 4) graduated exposure; and 5) relapse prevention. Materials are presented in a didactic (i.e., text-based with visual images) and case-enhanced learning format (i.e., educational stories demonstrate the application of skills) and include homework activities. Lessons are released gradually in a standardized order over 8 weeks. Phone calls will only be made if there is a significant clinical issue requiring therapist attention that cannot be addressed over email (e.g., sudden increase in symptoms). Therapists will spend ~15 mins. per week/per client.

Change in depression symptoms. 9 items are summed into a total score, with scores ranging from 0 to 27. Higher scores are associated with higher depression severity.

Change in anxiety symptoms. 7 items are summed into a total score ranging from 0 to 21, with higher scores indicating more severe self-reported levels of anxiety.

Change in panic symptoms. Items are summed into a total score. Total scores range between 0 and 28, with higher scores representing more severe self-reported symptoms of panic.