Our primary aim was to test the Interpersonal Theory of Suicide’s synergy hypothesis (i.e., the interaction between perceived burdensomeness and thwarted belongingness) in the proximal prediction of suicide ideation, while accounting for quadratic effects.
We used MTurk to recruit participants (N = 478) with a lifetime history of suicidal thoughts and behaviors; they completed two batteries of self-report questionnaires three days apart.
Contrary to the synergy hypothesis, only suicide ideation and the quadratic effect of perceived burdensomeness at Time 1 were significant predictors of suicide ideation at Time 2. The quadratic effect of perceived burdensomeness indicated a u-shaped function, whereby scores at or above the 80 percentile on perceived burdensomeness at Time 1 had increasingly strong, positive associations with suicide ideation at Time 2, while scores under the 80 percentile were not predictive of suicide ideation at Time 2. Also, thwarted belongingness and suicide ideation at Time 1 were significant predictors of perceived burdensomeness at Time 2.
These findings add to a growing literature that does not support the synergy hypothesis and suggests the importance of including nonlinear terms when examining the Interpersonal Theory of Suicide’s constructs.
© 2020 American Association of Suicidology.