Overgeneral memory retrieval (OGM) is defined as a difficulty recalling specific personal memories, and/or the tendency to recall non-specific memories, when asked to recall an event in response to emotional cue words. This research project examined the nature of cognitive processes underlying OGM in individuals with a history of trauma and depression. Regardless of the large body of existing research, the following points remain unclear: the course of OGM (e.g., the mechanisms underlying the maintenance of OGM); the reason why trauma history and depression are particularly relevant to OGM; and the relationships between a history of trauma, depression and OGM. To answer these points, the similarities and differences of OGM in individuals with a history of trauma and depression were examined through a series of studies. Prior to the main studies, the role of childhood trauma as opposed to adulthood trauma in OGM was examined in Study 1 (Ono & Devilly, 2013) based on the idea that OGM is a developmental memory deficit. As its significant relationship with OGM was found, childhood trauma became the focus of this research project.