This 8-week, pilot randomized, controlled trial to evaluate the benefits of transdiagnostic Internet-based CBT (iCBT) in young adults with MDD, SAD, PD or GAD. The investigators hypothesize that patients who receive iCBT will show significant improvement in anxiety symptoms and functioning, compared to a wait-list group. This pilot randomized controlled study will assess the efficacy of transdiagnostic iCBT in 60 young adults.

Unipolar depression and anxiety disorders (particularly social anxiety disorder [SAD], generalized anxiety disorder [GAD] and panic disorder [PD]) are among the most common forms of mental illnesses. They often have a chronic course, and are frequently associated with co-morbidities, significant disability, and poor quality of life. Published epidemiologic studies indicate that these conditions typically emerge during early adolescence and adulthood, and are often poorly recognized, resulting in delay of several years before help is sought. Such delay is often attributed to the non-recognition of the significance of the symptoms, lack of information on or access to services, and embarrassment and fear of stigma, but each effective early treatment can reduce co-morbidities and improve prognosis.

Cognitive behaviour therapy (CBT) is recognized as the single most effective psychological intervention for depression and anxiety, but accessibility is affected by therapist costs and long wait times for OHIP-covered services. Internet-based CBT (iCBT) is an innovative alternative with higher accessibility and cost-efficiency than group CBT, but with comparable efficacy. Transdiagnostic models of iCBT that treat depression, SAD, PD and GAD within one program have shown efficacy in preliminary trials and may offer even greater accessibility and economy, as several depressed and anxious populations can be treated with the same protocol. As a non-pharmacological treatment option enhanced by technological advances, iCBT is likely to appeal to tech-savvy young adults. However, it has not been evaluated specifically in a young adult population, thus far.

This 8-week, multi-site, randomized, controlled trial to evaluate the benefits of trandiagnostic iCBT in 60 young adults with unipolar depression and/or SAD, PD or GAD. We hypothesize that patients who receive iCBT will show significant improvement in depressive and anxiety symptoms and functioning, compared to a wait-list group.

Inclusion Criteria:

1. Age range (18-29 years).
2. Primary diagnosis of MDD, SAD, PD and/or GAD, per the DSM-IV-TR.
3. A score ≥17 on the first 17 items of the Hamilton Depression Rating Scale (HAM-D)55
4. A score ≥17 on the Hamilton Anxiety Rating Scale (HAM-A)56.
5. Score ≥50 on the Leibowitiz Social Anxiety Scale (LSAS),57 ≥10 on the Panic Disorder Severity Scale (PDSS)58 and/or ≥60 the Penn State Worry Questionnaire (PSWQ).59
6. Currently unmedicated or on stable and adequate doses of medication for at least 4 weeks.
7. Co-morbidities are allowed and will be documented.

Exclusion Criteria:

1. Primary diagnosis of any psychotic disorder or any other anxiety disorder (OCD, PTSD).