Cognitive accounts of depression and anxiety emphasize the importance of cognitive biases in the maintenance of disorders. One specific bias is the interpretation of ambiguous information. A negative interpretation bias is defined as a systematic tendency to interpret potentially ambiguous information in a negative rather than benign way and this bias has been associated with symptoms of depression. Research has led to the recent development of computerized cognitive bias modification (CBM) techniques to augment such biases and it has been suggested that CBM techniques may be useful as an adjunct to current treatments to enhance maintenance of treatment gains and minimize relapse rates. The fact that CBM procedures lend themselves to being delivered remotely, are cost-effective, and can be self-paced in ways that suit the patient make them an ideal candidate for inclusion in the Internet-based cognitive behavioural therapy (iCBT) programs currently offered through St. Vincent's Hospital and the University of New South Wales. Therefore, the primary aim of the current trial is to evaluate the acceptability and effectiveness of adding CBM procedures to the existing iCBT modules offered through St. Vincent's Hospital and the University of New South Wales. It is expected that iCBT + CBM will result in superior treatment outcomes as indexed by a standardized clinical battery.

Inclusion Criteria:

• Meet Diagnostic and Statistical Manual of the American Psychiatric Association - 4th edition (DSM-IV) criteria for Major Depressive Disorder,
• Internet access + printer access,
• Australian resident,
• Fluent in written and spoken English.

Exclusion Criteria:

• Current substance abuse/dependence,
• Psychotic mental illness (Bipolar or Schizophrenia),
• Current or planned psychological treatment during study duration,
• Change in medication during last 1 month or intended change during study duration,
• Use of Benzodiazepines,
• Suicidal.