• Negativistic, avoidant

  • Negativistic, avoidant, and dependent

  • Negativistic, avoidant, and antisocial

The first two overlapped with depressive/withdrawn temperament while the third overlapped with impulsive/aggressive temperament.

Among the impulsive/aggressive types, suicide often occurs in the absence of an affective disorder (Apter et al., 1995; 1991). Individuals with irritable/aggressive temperaments have increased risk of violence and suicide. Suicide among this group is associated with antisocial personality traits, impulsiveness, uncontrolled emotions, high novelty-seeking, alcohol and substance abuse, and histories of childhood adversity, including sexual abuse (Fergusson et al., 2000; Verona and Patrick, 2000).

Impulsivity (Eaves et al., 2000) and related sensation-seeking (Hur and Bouchard, 1997) show partial heritability related to physiological markers such as the Lewis red blood cell phenotype (Harburg et al., 1982), and a significant but modest association with the gene for a receptor of the brain chemical norepinephrine, the adrenergic alpha 2A receptor (Comings et al., 2000). Alterations in the serotonin system have also been implicated in studies of impulsivity’s relationship to aggression and suicide (Goldston, 2001; Lesch and Merschdorf, 2000; Mann et al., 2001; Verona and Patrick, 2000, see also Chapter 4).

Animal analog studies show that genetic strains with greater novelty-seeking/impulsivity are more susceptible to environmental insults (Piazza et al., 1991; 1993; 1996), with consequent increases in self-administration of addictive substances (Piazza et al., 1991; 1993; 1996). Other animal studies demonstrate that genetic influences on aggressive behavior interact with rearing environment, and that aggressive behavior and defeat experiences alter serotonin levels, future behavior, and genetic expression in the brain (Miczek et al., 2001; 1994; Nikulina et al., 1998; 1999; van Erp and Miczek, 2000). Such studies may provide models of how genetic and neurobiological aspects of impulsive/aggressive temperament interact with environmental factors to increase risks for suicide (see also Chapter 4).

The depressive/withdrawn personality traits are also termed “neuroticism.” This temperament is highly correlated with negative affect, poor regulation of emotions, and high anxiety, as well as suicide (Catanzaro, 2000; Goldsmith et al., 1990). High neuroticism was found linked with increased suicide attempts in a 21-year, prospective, study of 1265 children in New Zealand (Fergusson et al., 2000). Like those individuals at risk for suicide with the irritable/aggressive traits, those with high neuroticism who attempted suicide were also more likely to have experienced childhood trauma, including abuse and inadequate relationships with caretakers (see Chapter 5).

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