Depression (Major Depressive Disorder; MDD) has been dubbed "the common cold among the mental illnesses" and it is also a highly recurrent disorder. Secondary prevention has been identified as a key goal in the long-term management of depression. High recurrence rate suggests that there are specific vulnerability factors that increase people's risk for developing repeated episodes of the disorder. Preventive strategies should identify and ameliorate these factors to reduce the individual's risk of subsequent episodes. Biased attention for emotional stimuli is central to the cognitive model where increased sensitivity to negative cues is believed to fuel the negative thoughts and feelings in depression and play a key role in maintaining the illness. Selective biases in attention can be modified by a simple computerized technique; The Attention Bias Modification Task (ABM). This project aims to investigate whether ABM can reduce surrogate and clinical markers of relapse in a large group highly vulnerable to depressive episodes. The effects of ABM, immediately after the two weeks intervention, on three key risk factors for depression will be studied: Residual symptoms, cortisol awakening response and emotion regulation strategies. The participants will be followed up after 1 month, 6 months and 12 months. The hypothesis that ABM will reduce subsequent episodes of low mood over the following 12 months in this group in a manner predicted by early changes in these risk factors will be investigated. It will also be tested if such effects in the lab may be dependent on candidate genes which affect serotonin reuptake and which have been implicated in malleability and emotional learning. Effects on underlying neural correlates of emotion regulation will be studied in an fMRI experiment in a sub-sample and which will also be stratified by serotonin transporter genotype (see also NCT02931487). The predictive value of meta cognitions related to rumination and the possible mediating effects of automatic thoughts and perceived stress will also be investigated in a sub group (see also NCT02648165).

The characterization of the cognitive, genetic and neural mechanisms underlying the ABM effect will have key implications for future treatment development and combination with other treatment modalities like pharmacotherapy.

Inclusion Criteria:

• Nondepressed subjects (based on the MINI structured interview) with a history of major depression

Exclusion Criteria:

• Current or past neurological illness, bipolar disorder, psychosis or drug addiction.