Background: Suicidal ideation is a grave symptom of major depressive disorder (MDD), that can have long-lasting cognitive effects. Cognitive Reactivity (CR) is the reactivation of depressogenic...Show moreBackground: Suicidal ideation is a grave symptom of major depressive disorder (MDD), that can have long-lasting cognitive effects. Cognitive Reactivity (CR) is the reactivation of depressogenic cognitions by dysphoric mood states, after recovery. CR is important as it predicts relapse. Previous studies found that individuals who have contemplated suicide may be particularly vulnerable to reactivation of depressive cognitions; however, suicidal ideation was assessed retrospectively. The present study is prospective. Methods: Cohort study. Participants who met the DSM-IV diagnostic criteria for MDD were included if they no longer satisfied the criteria two years later (N = 943). CR scores during remission were compared between individuals who were not suicidal during their index (baseline) episode (SI-) (N = 346), versus those who were (SI+) (N = 597) — within which, a subcategory of those who attempted suicide in their lifetime (N = 152) was included. Results: During remission, SI+ participants had significantly higher hopelessness reactivity scores than SI- participants, even when factoring current depressive symptoms and suicidality, and anxiety comorbidity. Current hopelessness reactivity was significantly predicted by previous suicidal ideation, and to a lesser degree, feelings of worthlessness/guilt. Participants who had attempted suicide had significantly higher aggression reactivity, compared to without a history of suicidality. Limitations: Cognitive reactivity may have been influenced by the unaccounted disparity in participants’ most recent suicide attempt, and the number of previous depressive episodes. Conclusions: The results support the differential activation model of suicidality. Robust and strong longitudinal associations are drawn between suicidal ideation during depression, and a subsequent, distinct cognitive reactivity profile on the hopelessness dimension during remission. Given the profile specificity of cognitive reactivity, preventative measures for relapse are promising. Further research including the number of previous depressive episodes, suicide attempts and their recency may strengthen the validity of findings.Show less