Do Smokers Who Commit Suicide Have High Blood Levels of Nicotine?

To the Editor: Cigarette smoking is associated with a higher risk for suicide and attempted suicide (1, 2). In addition, an association between cigarette smoking and suicidal behavior across major psychiatric disorders may be related to lower brain serotonin function in smokers with depression (2). Unfortunately, no information is available concerning nicotine and cotinine levels in the body fluids of smokers who committed suicide.

We examined the nicotine and cotinine levels in the blood and urine of 36 forensic autopsy cases with no obvious putrefaction that were handled between October 2002 and March 2004. Our cases consisted of eight smokers who committed suicide (six men, 51–76 years of age, and two women, 54–79 years of age), eight smokers who did not commit suicide (seven men, 36–79 years of age, and one woman, 54 years of age), and 20 nonsmokers (15 men, 19–97 years of age, and five women, 62–82 years of age). One suicide case was present in the nonsmoking group. None of the suicide smokers consumed nicotine preparations or tobacco leaves.

Eight suicide smokers had high levels of nicotine and cotinine in their blood (mean=115 ng/ml, SD=49, and mean=405 ng/ml, SD=291, respectively) and urine (mean=1940 ng/ml, SD=2540, and mean=1170 ng/ml, SD=1570, respectively). In contrast, eight nonsuicide smokers had lower levels of nicotine and cotinine in their blood (mean=30.1 ng/ml, SD=17.7, and mean=122 ng/ml, SD=65, respectively) and urine (mean=383 ng/ml, SD=417, and mean=170 ng/ml, SD=86, respectively). Blood nicotine levels in our eight suicide smokers were significantly higher than in nonsuicide smokers (t=4.61, df=14, p=0.0004). Although urine nicotine level and blood and urine cotinine levels were higher in suicide than nonsuicide smokers, they did not achieve a level of statistical significance. In six of 20 nonsmokers, nicotine and/or cotinine originating from passive smoking were detected. Neither nicotine nor cotinine was detected in the remaining 14 cases.

Urae et al. (3) reported that habitual smokers with no psychiatric disorders who consumed 26 or more cigarettes per day had blood nicotine levels of 20.0–68.0 ng/ml (mean=35.2 ng/ml, N=34) in a free smoking experiment. Blood nicotine levels measured in our eight nonsuicide smokers were similar to their results.

Our data, although they are preliminary and limited in number, strongly suggest that a marked increase in cigarette smoking in persons with psychiatric disorders may be a sign of an imminent suicide attempt. Consequently, the smoking status of psychiatric patients may serve as a clinical sign of their mental status and provide an early warning sign of a possible suicide attempt.