gaps in our knowledge, strategies for prevention, and research designs for the study of suicide.

RISK AND PROTECTIVE FACTORS

Biological, psychological, social, and cultural factors all have a significant impact on the risk of suicide. The report reviews many of these risk factors individually, but the Committee emphasizes the need for an integrated understanding of their influence.

Over 90 percent of suicides in the United States are associated with mental illness and/or alcohol and substance abuse. Yet it is important to remember that as many as 10 percent of people who complete suicide do not have any known psychiatric diagnosis. This percentage appears higher still in non-Western societies such as China. It is also important to remember that over 95% of those with mental disorders do not complete suicide. The relationship between suicide and mental illness is a conundrum. Suicidality, although clearly overlapping the symptomatology of the associated disorders, does not appear to respond to treatment in exactly the same way. Depressive symptoms can be reduced by medicines without reduction in suicidality. And psychotherapy can reduce suicide without significant changes in affective symptoms.

Over 30 years of research confirms the relationship between hopelessness and suicide across diagnoses. Hopelessness can persist even when other symptoms of an associated disorder, such as depression, have abated. Impulsivity, especially among youth, is increasingly linked to suicidal behavior. Resiliency and coping skills, on the other hand, can reduce the risk of suicide. Research suggests that coping skills can be taught.

Biological changes are associated with completed and attempted suicide. Abnormal functioning of the hypothalamic-pituitary-adrenal (HPA) axis, a major component of adaptation to stress, has been shown to be promising for the prediction of future suicides, but not consistently for suicide attempts. Serotonergic function is reduced and noradrenergic function is altered in the central nervous systems of both suicide attempters and completers. Several lines of evidence, including adoption, twin, and family studies, point to a link between genetic inheritance and risk of suicide. Having a first-degree relative who completed suicide increases an individual’s risk of suicide 6-fold. The genetic liability may be linked to the heritability of mental illness and/or impulsive aggression. Since the heritability of liability to suicidal behavior appears to be on the order of 30–50%, interactions with social and cultural influences must also be significant.



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