Weinlander M M, Lee S H
J Psychol. 1976 Jan;92(1st Half):77-8. doi: 10.1080/00223980.1976.9921337.
The relationship between childhood onychophagia (finger-nail biting) and the mean age of suicidal and nonsuicidal veterans was investigated among 70 V.A. hospitalized males, diagnosed as personality disorders. The results show that the mean age of suicidal veterans was significantly lower than that of nonsuicidal veterans, and the childhood onychophagia variable, "focal suicide," significantly lowered the mean age of suicidal veterans, but did not significantly lower the mean age of nonsuicidal veterans.