Approximately 1 million persons worldwide commit suicide each year. In the United States, the number of deaths from suicide over the past 20 years exceeded the number of deaths from acquired immunodeficiency syndrome. More than 90 percent of persons who commit suicide have psychiatric illnesses; mood disorders are most commonly associated with suicide. Most persons with these disorders who commit suicide seek professional help in the month before their death; however, at the time of suicide, most are untreated. This suggests that the lack of treatment of mood disorders may contribute to the risk of suicide. Recent information adds to the concern that selective serotonin reuptake inhibitors (SSRIs) may increase the risk of suicide, particularly in children. There currently are no randomized trials that can prove or disprove this theory, and any such trial would be difficult to perform because of the large number of patients that would have to be treated for trends to be observed. Gibbons and colleagues used a national database to evaluate the relationship between antidepressant medication prescription and suicide rates.
Data on suicide rates were obtained from the National Center for Health Statistics of the Centers for Disease Control and Prevention. The data covered every county in the United States and were broken down by sex, race, and age group (i.e., five to 14 years, 15 to 24, 25 to 44, 45 to 64, and 65 years and older). Data on the use of antidepressants were drawn from a national pharmacy database that did not include hospital prescription information. The antidepressant prescription data were divided into three groups: tricyclic antidepressants (TCAs), SSRIs, and others. The main outcome measures were the suicide rate in each county and the impact of antidepressant use.
A regression model was used to adjust for age, sex, and race differences among counties, and the observed suicide rates matched well with expected rates (i.e., increase with age, higher in men, lower in blacks). The authors of the study found no significant relationship between the use of antidepressant medications and suicide rates. Prescriptions for SSRIs and new-generation non-SSRI antidepressants were associated with lower suicide rates. The suicide rate was higher in counties that had a higher use of TCAs. Suicide rates were higher in rural counties, which had fewer antidepressant prescriptions, lower income, and more prescriptions for TCAs. There was no significant change in suicide rates with regard to age and use of non-TCA antidepressants.
Although greater prescription use of SSRIs and new-generation non-SSRIs was associated with lower suicide rates in this study, and the use of TCAs was associated with an increase in suicide rates, the authors conclude that a direct causal relationship cannot be assumed. A high number of TCA prescriptions in any one county may be indicative of limited access to high-quality health care and other factors, and the association between lower suicide rates and SSRI or non-SSRI antidepressants may be attributable to the effectiveness of the medications, greater patient compliance, access to better-quality mental health care, and the lower toxicity of these medications in the event of a suicide attempt.