The 90% Statistic

Abstract

This chapter evaluates the centrality of mental illness in discussions of suicide and argues that the predominance of this perspective reflects confirmation bias, which is the tendency to search for and interpret information in a way that supports our beliefs and assumptions. Most people who are actively involved in suicide prevention learned that 90% of those who die by suicide were struggling with a mental illness at the time of their death. As a tool for diagnosing mental illness among individuals who cannot speak for themselves, however, the psychological autopsy method is vulnerable to confirmation bias. Instead of assuming that most or all individuals who die by suicide have a mental illness, a more balanced and accurate perspective would be that some individuals who die by suicide have a mental illness and some individuals who die by suicide do not. The chapter concludes that mental illness is only weakly correlated with suicidal behaviors and a much larger percentage of suicides than we may have traditionally recognized occur in the absence of mental illness.