早期発症対晩期発症自殺行動における社会的敗北への反応：実験的行動研究

Social defeat is often cited as a motive for suicide. The experience of defeat may arise from feeling dominated in a dyadic conflict or from losing status in a group. We hypothesize that sensitivity to dyadic defeat will be related to the onset of suicidal behavior in early or mid-life and sensitivity to loss of status, in late life.

The study's sample of 245 adults aged 50 years and older (mean = 63.2 years, SD = 7.4) comprised 42 early-onset and 32 late-onset suicide attempters (aged < 50 vs ≥ 50 years at their first suicide attempt), 114 depressed non-attempter comparisons, and 57 non-psychiatric comparisons. Using a validated rigged video game tournament task, we operationalized compensatory responses to the two forms of social defeat as point stealing from individual opponents (one-on-one defeat) and rank buying in the league table (loss of status in a group).

Early-onset attempters increased point stealing the most over time (χ²₃ = 22.37, p < .001), whereas late-onset attempters purchased more rank after losing trials than early-onset attempters and non-psychiatric comparisons (χ²₃ = 9.47, p = .024). Each effect was robust to adjusting for age and sex, other effects of interest, and to the exclusion of long-string responders.

Our behavioral findings suggest that socio-behavioral processes leading to suicide vary across the life cycle. While vulnerability to dyadic defeat could be suicidogenic for people of any age, loss of social status could play a role in suicidal crises specifically occurring in later life.