Abstract
Marked heterogeneity in suicide attempters has been observed, with earlier onset being linked to stronger heritability, more childhood maltreatment. Nitric oxide signalling system might be implicated in this relationship through its role in the stress response/adaptation. This study examined how NOS genetic variants and childhood maltreatment were associated with age at first suicide attempt (SA). Adult patients with SA history (N = 414) filled in the Childhood Trauma Questionnaire, and six functionally relevant NOS2 and NOS3 polymorphisms were genotyped. Analyses included χ2, Mann-Whitney U tests, Kendall's regression, multivariate linear and Cox survival regressions, and a moderation analysis. The NOS3 promotor 27-bp variable number tandem repeat (VNTR) bb homozygous state and childhood emotional abuse were independently associated with earlier age at first SA, which was robust after controlling for confounders [regression coefficient - 3.975, 95% CI -6.980 - (-0.970), p = 0.010, and - 1.088, 95% CI -2.172 - (-0.004), p = 0.049]. No interaction was observed. In the Cox proportional hazards model for age at first SA, the hazard ratio for patients with childhood emotional abuse and NOS3 27-bp VNTR bb was 0.533 (95% CI 0.394-0.720, p < 0.001) compared to patients without. Intermediate scores were observed with either only the risk genotype or only childhood emotional abuse. A graded relationship was also observed for repeated SA, family history of SA, and severe SA history. These results are preliminary due to a low statistical power and call for replication and further characterization of the role of nitric oxide system in the susceptibility to early-onset SB.