(NBC) - Antidepressants are the number one prescribed drug in America and it is estimated about every one in ten people is seeking treatment for depression at any given time.
But in a small percentage of people, the drugs that are supposed to make them happier actually increase the thoughts of suicide instead.
For the first time, researchers at the University of California, Los Angeles may know why.
Research psychologist Aimee Hunter of UCLA used what's called a "qeeg" machine to measure electrical activities in the brains of antidepressant takers.
She found that within 48 hours of taking the drugs, those who became more suicidal showed a 600 percent drop in brain activity compared to the brain activity in regular patients.
"This is the first time that anyone has demonstrated or identified a change in brain function that is related to worsening suicidality," Hunter said.
The hope is doctors will soon be able to use this simple tool to catch any brain alterations early on, so patients can be put on different drugs or taken off of them before it is too late.
Hunter said more studies to verify her findings are now in the works. She hopes within five years these "qeeg" machines will be widely available to doctors with depressed patients, especially underage patients who may be at higher risk.