Grant: Project Grant

Assessing suicide risk is clinically challenging given over 50% of individuals with Major Depressive Disorder (MDD) have suicidal thoughts, yet only 20% will make an attempt. This study will investigate why some people with MDD attempt suicide while others do not by exploring the behavioral and neurobiological mechanisms of pain processing. Based on current suicide theory, capability for suicide (CS) is a key construct to explain why suicidal ideation does not universally lead to attempt. CS is characterized by pain tolerance. Emerging evidence also shows that individuals who attempt suicide report increased pain tolerance. Our pilot data suggest this impairment may reflect abnormalities in the brain's pain processing network. We tested 20 MDD adults with current/history of suicidal behavior and 21 healthy controls. Self-reported CS correlated with connectivity in brain pathways essential for pain perception and modulation. CS also correlated with behavioural pain measures from cold stimuli (e.g., pain tolerance). We aim to build on this work exploring pain processing as a mechanism for suicide risk by directly testing brain activity during a pain task in the scanner. MDD patients who have suicidal ideation with suicide attempt history (n=55) and without (n=55) and healthy controls (n=55) will undergo a pressure pain task in the brain scanner and a cold pain task outside of the scanner. Brain activity and behavioural response to pressure pain will be compared across groups. Secondary aims are to determine whether behavioural pain processing measures are similar across different stimuli (pressure and cold), and whether CS correlates with behavioural and brain responses to pain. This research will provide the first evidence of neural pain processing differences associated with suicide attempt. In addition, testing pain tasks as an easy-to-measure proxy for CS paves the way to develop innovative tools (e.g. objective CS behavioural tasks) for clinical use.