Effective preventive strategies could reduce disability and the long term social and health complications associated with depression, but options are limited. Cognitive bias modification (CBM) is a novel, simple, and safe intervention that corrects the attentional and interpretive biases associated with depression.

To determine if CBM decreases the one-year onset of major depression in adults at risk.

This randomised controlled trial will recruit adults with subsyndromal depression living in Australia (parallel design, 1:1 allocation ratio). The intervention will be delivered via the internet over 52 weeks. The primary outcome of interest is the onset of a major depression according to DSM-IV-TR criteria. Secondary outcomes of interest include change in the severity of depressive (Patient Health Questionnaire, PHQ-9) and changes in attention and interpretive biases. Outcomes will be collected 3, 6, 9 and 12 months after randomisation.

Preliminary data on a subsample of 20 participants showed that the mean±SE PHQ-9 score of controls was 7.5±0.9 at study entry and 7.1±1.5 at week 6 (paired t-test=0.29, p=0.779), whereas the mean±SE score of active CBM participants was 7.4±1.0 and 4.4±1.1, respectively (paired t=6.00, p<0.001). The mean PHQ-9 difference between control and active CBM participants over 6 weeks was 2.6±1.5 points (t=1.79, p=0.090). One of 11 controls (9.1%) and 0/9 active CBM participants showed evidence of clinically significant depressive symptoms at week 6 (i.e., PHQ-9≥15).

By March 2015, 6-months preliminary data will be available on 165 participants.