When patients under age 24 are prescribed higher-than-recommended doses of antidepressants, they are more than twice as likely to attempt to hurt themselves, compared with their peers who are treated with the recommended dose, a new study concludes.

“If I were a parent, I definitely wouldn’t want my child to start on a higher dose of these drugs,” study author Dr. Matthew Miller of the Injury Control Research Center at the Harvard School of Public Health in Boston told HealthDay.

The findings are published in JAMA Internal Medicine.

The Food and Drug Administration (FDA) issued a warning in 2004 about the risk of suicide in children and adolescents treated with antidepressants known as selective serotonin reuptake inhibitors (SSRIs). The FDA warning came after a government study found young people who took SSRIs were twice as likely to hurt themselves, compared with those who took placebo pills. In 2007, the FDA expanded its warning to include anyone under age 25.

The new study is the first to look at the rate of suicide risk by drug dosage, the article notes. The researchers evaluated data from more than 162,000 patients with a diagnosis of depression, who began taking an SSRI between 1998 and 2010. The study looked at patients who took Celexa, Zoloft or Prozac. Almost 18 percent of patients began taking SSRIs at doses that were higher than recommended.

The researchers found among patients younger than 24, the rate of self-harm was 32 per 1,000 for those taking a higher-than-recommended dose, compared with 15 per 1,000 for those taking the recommended dose. They did not find a significant increase in the risk of self-harm among patients over age 25 who took a higher-than-recommended dose.