Depression and serum cholesterol are the strongest correlates of suicidal ideation in combat-related post-traumatic stress disorder

Background

Suicidal ideation in chronic combat-related post-traumatic stress disorder (PTSD) is usually approached through overall PTSD severity, depressive symptoms and behavioural dysregulation. Serum lipids have also been linked to depression, aggression and suicidality, possibly through serotonergic mechanisms, but their relative contribution to suicidal ideation within PTSD remains unclear.

Aims

We examined the relative importance of depressive symptoms, agitated behaviour, PTSD severity and total serum cholesterol for suicidal ideation in male combat veterans with chronic PTSD.

Methods

This cross-sectional analysis included 203 male outpatients with chronic combat-related PTSD, diagnosed according to both ICD-10 and DSM-IV criteria. Psychiatric premorbidity and comorbidity were excluded using the Mini-International Neuropsychiatric Interview. Suicidal ideation was assessed with the Beck Scale for Suicidal Ideation (BSS), depressive symptoms with the 17-item Hamilton Depression Rating Scale (HDRS-17), agitated behaviour with the Corrigan Agitated Behaviour Scale (CABS), and PTSD severity with the Clinician-Administered PTSD Scale (CAPS). Total cholesterol was calculated as the mean of two fasting serum measurements. We fitted linear regression with robust standard errors for standardised BSS score and logistic regression for high suicidal ideation, defined as BSS ≥ 20, the sample upper quartile. Core predictors were standardised HDRS-17, CABS, CAPS and total cholesterol. Models were adjusted for age, body mass index, education, having a steady life partner, work status and antidepressant class. Conditional dominance analysis quantified the relative contribution of the four core predictors to explained variance.

Results

Median age was 47 years (IQR 43–54). Median scores were 13 (IQR 7–19) for BSS, 18 (IQR 16–22) for HDRS-17, 19 (IQR 17–32) for CABS and 70 (IQR 65–76) for CAPS. Forty-seven participants (23.2%) had high suicidal ideation. In the adjusted linear model, explained variance was 48.4% (adjusted R² = 45.2%). Higher HDRS-17 (standardised β = 0.41, p < 0.001) and lower total cholesterol (standardised β = −0.37, p < 0.001) were independently associated with higher BSS score. CABS (standardised β = 0.11, p = 0.108) and CAPS (standardised β = 0.03, p = 0.599) were not independently associated with continuous BSS score.

Dominance analysis attributed 48.1% of the explained variance from the core predictors to HDRS-17, 45.5% to total cholesterol, 6.3% to CABS and 0.2% to CAPS. In logistic regression, high suicidal ideation was associated with HDRS-17 (OR per SD = 2.14, 95% CI 1.31–3.49, p = 0.002), CABS (OR = 1.75, 95% CI 1.10–2.78, p = 0.019) and lower total cholesterol (OR = 0.31, 95% CI 0.13–0.76, p = 0.010), but not CAPS (OR = 0.87, 95% CI 0.56–1.34, p = 0.520). Apparent AUC was 0.89 (bootstrap percentile 95% CI 0.83–0.94). Conclusions were unchanged in sensitivity models additionally adjusted for anxiolytic and hypnotic class.

Conclusions

In male combat veterans with chronic PTSD and no psychiatric comorbidity, suicidal ideation was driven mainly by depressive symptoms and lower total cholesterol rather than by global/general PTSD severity. Agitated behaviour helped classify high suicidal ideation but explained little of its continuous burden. These cross-sectional findings require longitudinal validation.

References

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