Children and young adults may have an increased risk of suicidal behavior if they begin taking antidepressants at higher than normal doses.

Starting children and young adults on high doses of antidepressants may increase their risk of harming themselves deliberately, according to a new study. These results support earlier research by the Food and Drug Administration, but leave open the question of why higher than normal doses could increase the risk of suicidal and other harmful behavior.

The study, published today in JAMA Internal Medicine, involved 162,625 people between the ages of 10 and 64 who had been diagnosed with depression. All of these people were new users of selective serotonin reuptake inhibitors (SSRIs)—a category of antidepressant drug that includes Prozac—and had not been treated with any antidepressants in the past year.

By looking at a wide age range, researchers from the Harvard School of Public Health and other institutions found that children and young adults who were given higher than typical doses of antidepressants at the start of their treatment were twice as likely to hurt themselves deliberately, compared to those given standard doses. People ages 25 to 64 years old, however, showed no increased risk of suicidal behavior when treated with higher doses of antidepressants.

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While the study did not investigate why higher doses would increase the risk of suicidal behavior, some mental health professionals think it results from a convergence of many factors.

“It’s no surprise to me that the cut-off [age] is 25,” says clinical psychologist Deni Carise, Ph.D., Chief Clinical Advisor for Sierra Tucson. “There’s a very clear reason for that. That is the age at which the frontal lobe more fully develops.”

One function of the brain’s frontal lobe is impulse control. Because the frontal lobe of teenagers and young adults is still developing, they are more prone to impulsive behavior, so combining this with depression and antidepressants may be enough to trigger self-harm.

“Sometimes, suicide isn’t primarily about depression,” says Carise. “Sometimes, it’s a result of an intersection between hopelessness with impulsivity and an increased energy that might be found from the initial benefits of antidepressants.”

Higher doses of antidepressants can provide a boost of energy at the start of treatment, but the type of medication prescribed could also play a role, as well—again, something not examined in this study.

“Some antidepressants work better for certain people and different ones for other people,” says Carise. “So if you get the right one, and bring up those blood levels very quickly, you do want to watch the person much more carefully.”

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In the new study, researchers found that 18 percent of people were treated with an initial dose of antidepressants higher than that recommended by 2007 American Academy of Child and Adolescent Psychiatry (AACAP) guidelines. These suggest starting with a low dose of antidepressants for the first four weeks. Only then, after carefully monitoring the patient, should doctors consider a higher dose. Because researchers didn’t examine this factor directly, it’s not clear why some doctors prescribed a higher dose initially.

“They may have had better success with slightly higher doses,” says Carise. “The doses weren’t out of range—they weren’t wildly different. They’re still within kind of a normal range, but I think that the range should be looked at again.”

In spite of the increased risk of suicidal behavior among children and teens who were prescribed higher doses of antidepressants, the benefits of these medications are still clear. This study and other others like it, however, recommend caution.

“I think we really do need to be really careful about this, and really you’re walking a tightrope,” says Carise. “You have a kid that’s profoundly depressed. You want to get them some relief, but you also don’t want to do anything that could increase their likelihood of suicide.”

This means balancing the risks and benefits of antidepressants, along with carefully choosing the dose and type of drug. Also, given that most suicidal behavior in the study occurred within the first three months of treatment, doctors should more closely monitor their patients for behavioral changes during that time.

“You don’t want these kids to have to suffer,” says Carise. “You really want to get them some help, but you want to do it blending caution with the desire to give them effective medication to help them with their depression, while combining it with counseling.”

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