Q. What causes people to take their own lives?

A. There is no one cause of suicide - it is the result of a combination of factors. Current thinking falls into three major categories: biological, psychological and social. Biological theories address the possibility that there are physiological factors, such as an imbalance of neurotransmitters - serotonin especially - that create a predisposition toward suicidal behavior. The role of biology in depression, aggression and impulsive behaviors in suicide attempts and completed suicides is being studied.

With respect to the psychology of suicide, no theory is predominant. But an interesting possibility is the role played by attachments in early development and the ability of individuals to form and maintain stable relationships. Disruptions in relationships increase the risk of depression and also the risk for suicide in some groups.

Social theories can be traced to the work of Emile Durkheim in the late 19th century. Durkheim hypothesized that connectedness of people to their society and the meaning that they find in their larger social contexts are important factors in suicide.

All three theories are important ways of thinking about suicide, and they all have implications for prevention and intervention.

Q. How are the factors that contribute to completed suicides investigated?

A. Most data on risk factors for suicide come from "psychological autopsy" studies. These studies reconstruct circumstances surrounding a suicide by talking with family members, friends, and sometimes employers and health care providers. Psychological autopsy studies also often involve a review of medical records. Using this, a person's background, developmental history, symptoms, illnesses, stressors, and social circumstances help form a qualitative understanding of the person prior to suicide.

In an increasing number of studies, this information is used to determine whether there are patterns in the characteristics that distinguish people who commit suicide from similar people who are not suicidal. These studies offer a rich understanding of people who typically have not been seen in mental health settings prior to their deaths.

Other types of studies are being conducted as well. These include studies over time of large numbers of people in the general population, a small number of whom eventually take their own lives, or attempt to do so. This makes it possible to gather information prior to suicide attempts or completions and to identify factors related to increased risk.

Q. Based on existing research, who is most likely to die by suicide?

A. Although specific risk factors have been identified, it is difficult to predict who will be a victim of suicide because most people with these risk factors do not try to take their own lives. It appears that a combination of factors contributes to suicide.

The profile of people at risk for suicide also changes somewhat across the life course. Many younger people struggle with issues of relationships, financial problems, problems with drug and alcohol, legal problems and chaos in their lives in general. In middle age, suicide risk appears to be related to relationship problems, substance abuse disorders and psychotic illness. In later life, people have generally been survivors, so the issues are a little different. Risk appears to be related to depression, the inability to cope with the crescendo of stressors having to do with loss and life change, and the absence of sufficient social support.

Q. Are there other factors that distinguish suicide risk and suicide completion in older adults?

A. The rate of suicide among older people in the United States is higher than any other age group. This comes mostly from the very high rates of suicide among white males in later life. Males age 85 and up are at highest risk for suicide - about six times higher than the nation as a whole. The pattern is different for women. Although women attempt suicide more often, rates of completed suicide are much lower for women than for men.

Rates tend to peak in midlife, then remain stable or decline slightly, for women in the United States.

Older people who kill themselves are less likely than younger suicide victims to have attempted it previously. Also, older individuals who take their own lives are more likely to have suffered from a depressive illness than people who kill themselves at younger ages.

Q. What are some characteristic signs of depression in later life?

A. It is important to distinguish between depression or sadness as a temporary mood and depression as an illness. The illness is often called clinical depression. Its characteristics include loss of interest in activities, difficulty concentrating, low energy, increases or decreases in appetite, sleep disturbances, hopelessness or a bleak outlook toward the future, sadness, guilt and thoughts of suicide or death. In older people, depressive illness may be more likely to express itself in loss of energy and loss of interest rather than feeling sad or feeling like crying.