Neurobiology of adult and teenage suicide

Suicide is a major public health concern worldwide (Botsis et al 1997). About 30,000 people die of suicide in the USA and about 1 million worldwide (Botsis et al 1997; Goldsmith et al 2002). In the United States, suicide is the third leading cause of death in teenagers (Singh et al 1996). There are several risk factors for suicide, including the presence of depression (Lonqvist 2000) and other mental disorders (Caldwell and Gottesman 1992; Harris and Barraclough 1998; Lonqvist 2000; Moscicki 1997; Weissman et al 1989) and substance and alcohol abuse (Hlady and Middaugh 1988). Hopelessness (Beck et al 1993), stress (Westrin 2000), and impulsive-aggressive traits are among other risk factors (Brent et al 1999; Brent et al 1993; Linnoila and Virkkunen 1992). Recent studies also suggest that a family history of suicide and genetic and abnormal neurobiology may also be important risk factors for suicide (Ernst et al 2009; Mann 2003). There is evidence to suggest that some factors associated with adolescent suicide may be different from adult suicide (Brent et al 1999; Zalsman et al 2008). Although impulsive-aggressive behavior is a common risk factor for both adult and teenage suicide, aggression and impulsivity are traits highly related to suicidal behavior in adolescents (Apter et al 1995). Higher levels of impulsive aggressiveness play a greater role in suicide among younger individuals with importance decreasing with age (Brent et al 1993). Brent et al.(1993) have also shown that adolescents with aggression and conduct disorders may be suicidal even in the absence of depression. Psychosocial factors associated with adolescent suicide, such as stress and contagion, bullying and peer victimization (Brunstein et al 2008; Bursztein and Apter 2009; Klomek et al 2008) may also be different from adults. Alcohol and drug abuse contribute significantly to the risk of suicide in teenagers (Apter et al 1990; Apter et al 1995). Additional potential contributors to suicidal behavior in depressed adolescents are early defined traits such as temperament and emotional regulation. One study suggests (Tamas et al 2007) that suicidal youth are characterized by highly maladaptive regulatory responses and low adaptive emotional regulation responses to dysphoria. In the USA, as in many countries of the world, older adults are at greater risk for suicide; of the 35,000 people who died by suicide in the USA, more than 5,000 are among people older than 65 years (CDCPrevention 2007). Based on psychological autopsy (PA) studies it is estimated that mood disorder was the most common disorder among these cases (Conwell et al 1996). Hopelessness, stress (relationship and financial problems) are other risk factors. Biology of elderly suicide is not well studied. For suicidal behavior in elderly see review by Conwell and Thompson (2008). Neurobiological studies in suicide have been performed either in patients with suicidal behavior or in the postmortem brain of suicide victims. In this chapter, we will primarily focus on the major neurobiological findings in suicide related to serotonin and noradrenergic mechanism, signal transduction pathways, hypothalamic adrenal pituitary axis (HPA) dysfunction, and inflammatory markers (cytokines in the postmortem brain). We will also briefly discuss the evidence from studies of suicidal patients, specifically the 5HT system leading to these studies in postmortem brain.