Retrieval-induced Forgetting in Major Depressive Disorder with Exploration of Smoking Habits and Mindfulness

Background : Major depressive disorder (MDD) is associated with impairments in neuropsychological functioning. A key mechanism in memory retrieval is the process of inhibiting information that is not relevant to the specific memory, termed retrieval-induced forgetting (RIF). In MDD, attenuated RIF has been observed, in which related memories are not suppressed. The effect is proposed to be mediated by inhibitory functions, and associations with rumination have been observed. Whether the neuropsychological functions of verbal learning capacity and capacity for mindfulness are associated with RIF has not been examined. Methods : Participants were 65 MDD (mean age 46.4 years) and 65 healthy controls (mean age 42.4 year). Participants completed a RIF task and measures in depressive severity, verbal learning, mindfulness and rumination. Results : MDD participants demonstrated significant attenuation in RIF in comparison with healthy participants. Verbal learning and mindfulness were positively correlated with RIF, while increased depressive severity and rumination further attenuated RIF in MDD. Conclusions : Attenuated RIF is evident in MDD which is further attenuated by increasing depressive severity and rumination, while verbal learning ability and capacity for mindfulness were associated with restored RIF. These findings support clinical interventions which promote a state of relaxed self-awareness in MDD.