Although the relationship of trait impulsivity and suicidal behavior is well established, its relationship with suicidal ideation and its fluctuation still remains unclear. Our aim is to examine (1) the relationship of trait impulsivity and suicidal ideation and behavior in the context of the Interpersonal Psychological Theory of Suicide (IPTS) and (2) the association of trait impulsivity with the fluctuation of suicidal ideation in an inpatient sample with unipolar depression.
Eighty-four inpatients with unipolar depression and current and/or lifetime suicidal ideation were assessed with a baseline assessment including trait impulsivity, suicidal ideation, suicidal behavior and the constructs of the IPTS. Seventy-four of these patients underwent a 6-day ecological momentary assessment (EMA) with 10 assessments per day across six days assessing passive and active suicidal ideation. Mean squared successive differences (MSSD) across EMA assessments of suicidal ideation were calculated to test fluctuation as an indicator of temporal variability. Correlation analyses were conducted to test the associations.
There were no associations of trait impulsivity with suicidal ideation, thwarted belongingness and perceived burdensomeness, except the rather low but significant association between thwarted belongingness and the attention subdomain of trait impulsivity (r = 0.23*, p ≤ 0.05). Moreover, trait impulsivity showed a significant positive correlation with capability for suicide but not with the two subdomains of capability for suicide. The only significant but rather low correlation was identified between the motor aspect of trait impulsivity and fearlessness about death (r = 0.26, p ≤ 0.01). Suicidal behavior showed a positive correlation with trait impulsivity, but not with the different subdomains of trait impulsivity. Trait impulsivity showed a significant correlation with the MSSD of passive suicidal ideation (r = 0.26, p ≤ 0.05), but not with active suicidal ideation. Furthermore, the motor aspect of trait impulsivity (BIS motor) showed a significant correlation (r = 0.32, p ≤ 0.01) with the MSSD of passive suicidal ideation, but not with active suicidal ideation or the MSSD total score.
Overall the findings are in line with our assumptions and the IPTS and underline that trait impulsivity is related to suicidal behavior and the fluctuation of suicidal ideation, but not to suicidal ideation itself. Thus, trait impulsivity seems to act as a distal risk factor via capability for suicide and it seems to play a role for the dynamics of suicidal ideation. The results have to be investigated in larger samples, with a higher risk of suicide and in prospective studies. Moreover, the role of the fluctuation of suicidal ideation for the prediction of suicide risk should be investigated in future studies.