COgnitive bias modification to Prevent dEpression (COPE trial)

Cognitive bias modification (CBM) delivered via the internet over 12 months: 3 sessions/week during first 4 weeks, 2/week up for an additional 4 weeks, then 1/week up to week 26, once per fortnight up to week 38, and once per month up to week 52. Eligible participants will be randomly allocated to one of 2 treatment arms: sham or active CBM. CBM sessions will be delivered over a period of 52 weeks (1 year): three times per week for the first 4 weeks, twice weekly for the next 4 weeks (up to week 8), once weekly for the next 18 weeks (up to week 26), once per fortnight for the next 12 weeks, and once per month for the remainder of the follow up period (up to week 52). This delivery schedule is designed to achieve rapid bias modification though initially intensive training, while also encouraging maintenance of the resulting cognitive change through sustained exposure to CBM across an extended period, and by phasing out rather than abruptly terminating the intervention. Each CBM session will be of 40-minute duration, and will be accessed through a password-protected internet site. They will deliver CBM designed to reduce attention to negative information (CBM-A, 20 minutes) and to reduce the negative interpretation of ambiguous stimuli (CBM-I, 20 minutes). On each session, participants will be presented with a pair of emotionally-toned facial images (sad vs neutral or happy) for 500 ms, which will then be replaced by a small white probe (vertical or horizontal line), appearing in the screen position previously occupied by one of these stimuli. Participants will be instructed to use their keyboards to indicate the orientation of this probe as quickly as possible ('V' for vertical, 'H' for horizontal). The probe will then disappear and will be replaced, after 1 second, by another stimulus pair that will commence the next trial. The time to discriminate probe identity will be recorded automatically. In the active CBM-A condition all probes will appear in the opposite screen area from that of the negative stimulus (avoid negativity), while in the control condition probes will appear equally often in the area of the negative and non-negative stimuli. The second half of each 40-minute session will deliver CBM-I using single words and short textual scenarios as ambiguous stimuli. On each trial this ambiguous stimulus will first be presented (e.g. word ‘growth’), followed, 500 ms later, by a fragment of a word that is semantically consistent with one or other meaning of the preceding ambiguity (e.g., ‘t_mour’ or ‘gr_ater’). Participants will be instructed to complete this fragment to yield a word consistent with the meaning of the initial word or sentence, using their keyboard to enter the letter missing from the fragment. The time to solve the word fragments will be recorded automatically. In the active CBM-I condition all fragments will yield only words consistent with non-negative interpretations of the preceding ambiguity, while in the control CBM-I condition fragments will equally often yield words consistent with the negative and non-negative interpretation of this ambiguity. A large bank with thousands of faces, words and textual scenarios that have already been used in other studies is available, and the computer programs are ready for use. Adherence will be monitored via CBM login log records and the number of completed sessions.