Of the 701 participants with follow-up data, 128 had made a suicide attempt during the first seven years of follow-up. This includes 6 participants who committed suicide, as reported to us by a family member and/or verified by death certificate. Seventy four attempters (58% of attempters) reported attempts in multiple intervals. Thirty-nine participants reported a suicide attempt during the first 6 months of follow-up. Twenty participants reported a first attempt (8 repeat attempters) between months 7–12; 34 first (13 repeat) attempts in the 2nd
year, 9 first (19 repeat) attempts in the 3rd
year, 9 first (11 repeat) attempts in the 4th
year, 5 first (8 repeat) attempts in the 5th
year, 6 first (14 repeat) attempters in the 6th
year, and 7 first (7 repeat) attempts in the 7th
year. Among those who reported a suicide attempt, 74.4% met criteria for borderline PD compared to 26% who reported no suicide attempts (Χ2
)=108.3; p<.001). Avoidant PD was also more prevalent among suicide attempters compared to non-attempters (60.5% vs. 46.9%; Χ2
)=7.8; p=.005), while the rate of OCPD was significantly lower among attempters (24% vs. 43.2%; Χ2
)=16.13; p<.001). The most frequently observed baseline Axis I disorders among suicide attempters during follow-up were major depressive disorder (77.5% attempters vs. 77.8% non-attempters; NS), substance abuse/dependence (54.3% attempters vs. 32.9% non-attempters; Χ2
)=20.7; p<.001), alcohol abuse/dependence (58.1% attempters vs. 36.2 non-attempters; Χ2
)=21.1; p<.001), and posttraumatic stress disorder (49.6% vs. 26.0%; Χ2
)=27.6; p<.001). Less frequently reported, but statistically significant, was panic disorder (36.4% attempters vs. 25.2% non-attempters; Χ2
depicts data on demographics data for the participants who have and have not reported a suicide attempt during follow-up. The only significant demographic difference between these groups was sex (Χ2
)=6.68; p=.01), with more women reporting suicide attempts. There were no significant differences in age, education level, race/ethnicity, marital status, and employment status at baseline between attempters and non-attempters.
Demographic Data by Suicide Attempt (SA) Group
As an initial step to determine the degree of intercorrelation between variables, bivariate Pearson correlations were calculated among all trait predictors (). Our main higher order predictors, negative temperament and disinhibition, were significantly correlated (r=.20; p<.001). The tolerance (0.96) and VIF (1.04) indices suggest that the degree of collinearity is not problematic for regression analyses. Similarly, though several of the lower order impulsivity trait predictors were significantly correlated with NT, none indicated problematic collinearity.
Correlation Matrix for Trait Predictor Variables at Baseline
A series of Cox proportional hazards regression analyses (univariate, test of interactions, multivariate) was conducted to compare the extent to which NT, DIS, and facets of impulsivity prospectively predicted individuals who made a suicide attempt. Univariate analyses revealed that all were significant except for excitement seeking (). Negative temperament score was higher among suicide attempters compared to non-attempters, and significantly predicted suicide attempts during follow-up (HR=1.11, p<.0001). Similarly, scores on SNAP disinhibition (HR=1.07; p<.0001), impulsivity (HR=1.10, p<.0001), aggression (HR=1.06, p<.0001), and NEO impulsivity (HR=1.06, p=.001) were higher among suicide attempters and prospectively predicted suicide attempts. Scores on NEO self-discipline and deliberation were lower among attempters and prospectively predicted suicide attempts during follow-up (HR=0.96, p=.002 and HR=0.91, p<.0001 respectively).
Univariate Analyses of Trait Predictors and Comparison to Non-Clinical Sample
The second set of analyses, tests of interaction terms, found only a marginally significant interaction (not significant with Bonferroni correction) for SNAP IMP by SNAP AGG (HR=1.03, p=.02) suggesting that these traits exacerbate each others effects on suicidal behavior. The interaction between SNAP NT and SNAP DIS was not significant (HR=1.01, p=.48), and the interaction between sex and NT and sex and DIS, and CSA and NT and CSA and DIS were not significant in predicting suicide attempts during follow-up.
depicts results from the full model Cox proportional hazards regression analyses. The first model contains our primary trait predictors, NT and DIS, and covariates. Only NT remained significant (HR=1.08; p<.0001) and DIS was not significant. To further elucidate these findings, we examined lower order scales of impulsivity (IMP) and aggression (AGG) from the SNAP, as well as facets from the NEO; impulsivity (N5), self-discipline (C5), deliberation (C6), and excitement seeking (E5). While IMP, AGG, N5, and C5 were all significant in univariate analyses, they were not significant in multivariate analyses with NT and covariates. SNAP Impulsivity was marginally significant (HR=1.06, p=.0135), but did not meet our Bonferroni corrected significance level of p=.006. However, NEO C6, corresponding to lack of planning/premeditation, was significant in the full model multivariate analyses. In each of these full models with impulsivity facet and covariates, Negative Temperament and covariates of CSA, course of SUD, and course of MDD remained significant.
Cox PH Regression Analyses of Prospective Assessed Personality Traits and Covariates as Predicttors of Suicide Attempts.