Moderating effect of avoidance on the relationship between depression and suicidal ideation across different types of trauma exposure

Background Suicidal ideation following trauma exposure is frequently associated with depressive and post-traumatic stress disorder (PTSD) symptoms; however, the interactive effects of depression and distinct PTSD symptom clusters on suicidal ideation remain poorly understood. Aims To examine whether specific PTSD symptom clusters – namely intrusion, avoidance and hyperarousal – moderate the association between depressive symptoms and suicidal ideation, and whether these effects vary across different trauma types. Method Medical records of 127 psychiatric out-patients with a history of at least one traumatic event were analysed. All participants had completed the Hamilton Rating Scale for Depression, the Impact of Event Scale-Revised, and the suicidal ideation item of the Beck Depression Inventory II. Trauma types were categorised into early versus late, single versus multiple, and interpersonal versus non-interpersonal. Results Hierarchical regression analyses identified a significant moderating effect of avoidance symptoms on the relationship between depression and suicidal ideation ( β = 0.19, P = 0.012), whereas intrusion and hyperarousal symptoms did not show such effects. Specifically, higher levels of avoidance were associated with a stronger positive relationship between depression and suicidal ideation. This moderating effect was observed only among individuals with late ( β = 0.28, P = 0.002), single ( β = 0.29, P = 0.002) or non-interpersonal trauma ( β = 0.34, P = 0.018); it was not evident among those with early, multiple or interpersonal trauma. Conclusions These findings underscore the relevance of targeting avoidance symptoms to mitigate suicidal ideation, particularly in individuals with late-onset, single-incident or non-interpersonal trauma exposure. Exposure-based therapeutic interventions may offer particular benefit for reducing suicidal ideation among trauma-exposed individuals with depressive symptoms.