May 02, 2014 09:08 AM EDT By Staff Reporter, UniversityHerald Reporter

High dose of antidepressants increases suicide risk among children and young adults during the first three months of treatment, according to a Harvard School of Public Health study.

Researchers said that those who pop antidepressants including Selective Serotonin Reuptake Inhibitor (SSRIs) at higher doses were twice likely to attempt suicide than their peers who consume at average or typical prescribed doses.

Previous studies showed SSRI antidepressants increased risk of suicidal thinking and behavior in children and teenagers. The conclusions incited the U.S. Food and Drug Administration to issue a warning about the risk in 2004. The agency later expanded the warning to young adults up to the age of 25.

The warnings have not been well-accepted from all sections of medical society as SSRIs antidepressants have been found to effectively treat anxiety and depression.

The recent study does not determine whether SSRIs heighten the risk of suicide. Instead, the researchers wanted to find out how different doses affect suicide risk and whether the risk was based on patient's age.

"The design of the study was meant to really address the question, does dose matter?" Dr. Matthew Miller, an associate professor and lead author of the study, said, npr reports.

For the study, the researchers analyzed data from 162,625 patients suffering from depression, aged between 10 to 64 years, who received SSRIs antidepressant treatment at modal or higher than modal doses from 1998 to 2010.

The researchers found that the rate of suicidal behavior (deliberate self-harm or DSH) among children and adults (24 years or younger) who were associated with higher doses of antidepressant was twice when compared to a group of patients who were given the normal prescribed doses.

"It certainly is one more piece of information that should make doctors reluctant to start younger patients on high doses," Miller said, "even if those doses are within the therapeutic range."

The researchers also found that for adults 25 to 64 years old, the risk for suicidal behavior was absent.

"Considered in light of recent meta-analyses concluding that the efficacy of antidepressant therapy for youth seems to be modest, and separate evidence that dose is generally unrelated to the therapeutic efficacy of antidepressants, our findings offer clinicians an additional incentive to avoid initiating pharmacotherapy at high-therapeutic doses and to monitor all patients starting antidepressants, especially youth, for several months and regardless of history of DSH," the researchers said in a press release.

The study, however, did not provide answers to some key questions including why higher doses lead to an increased suicide risk.

The finding is published in JAMA Internal Medicine.              

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