Background: Self-generated thoughts (SGTs), such as during mind wandering, occupy much of our waking life. Individuals with Major Depressive Disorder (MDD) are less in the "here and now" and prone to rumination. Few studies have looked at SGTs in depression using experience sampling methods and no study has so far investigated the specific contents of depressive SGTs and how they vary from one time point to another.
Methods: MDD patients (n=25) and matched healthy controls (n=26) performed an established mind wandering task, involving non-demanding number discriminations. Intermittent probe questions ask for participants' current SGTs, that is, how off-task the thoughts are, how positive or negative, self- or other-related, and past- or future-oriented.
Results: Multi-level modelling revealed that MDD patients engaged in more mind wandering than healthy controls. Their SGTs were predominantly negative and less positive, more self-related and past-oriented. Strongest predictor of depressive SGT was the decreased positive valence of thoughts. MDD patients' future and past-oriented thoughts were particularly more negative compared to healthy controls. Within MDD patients, the less positively valenced thoughts they had and the less variable these thoughts were, the more depressive symptoms they showed.
Limitation: No other measures of rumination and worry were used.
Conclusion: MDD patients show a very specific SGT pattern, possibly reflecting ruminative and anxious thoughts. This SGT pattern in depression might represent a useful state marker and even constitute an etiological factor of this debilitating disease, considering the importance of current SGT on and individual's cognitive processes and affective states.