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Published on: March 20, 2017
Geographic proximity is associated with transmission of suicidal behaviour among siblings
A C Edwards1,2, H Ohlsson3, E K Mościcki4
1Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA.
Objective:
The aim of this study was to clarify the role of 'contagion', or social transmission, in risk of suicidal behaviour (SB) among siblings.
Methods:
We followed Swedish sibling pairs until one of them (S1; N = 111,848) was registered for a suicide attempt or completion. We tested the effect of geographic proximity between siblings on risk of a first SB registration of S1's sibling (S2). To control for familial confounding, we conducted complementary analyses of sibling trios (N = 701), comparing risk in different siblings as a function of their respective proximity to S1.
Results:
The best-fitting model across sibling pairs included an effect of distance between siblings (HR = 0.96, 95% CI = 0.93-0.99). Hazard ratios declined quickly up to 25 km and largely stabilized beyond 150 km. Across all pairs, a larger age difference between siblings was associated with reduced SB risk (HR = 0.96 95% CI = 0.93-0.98). Findings were consistent within the sibling trios.
Conclusions:
Consistent with the concept of suicide contagion, risk of suicidal behaviour subsequent to a sibling's suicide completion or attempt is higher as a function of sibling closeness. These findings are robust to potentially confounding familial factors.
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