Over the past five years, an increasing number of studies have pointed to the rare but serious risk of suicidal thoughts that can accompany new antidepressant treatments. Close monitoring is currently the only clinical option, but a new technique--one that measures and analyzes electrical activity of the brain--could one day predict which people might be most susceptible to antidepressant-induced suicide.

While uncommon, the gravity of suicide risk was enough to prompt the U.S. Food and Drug Administration to place a "black box" warning on multiple antidepressant labels. So in order to tease out those individuals at highest risk, researchers at the University of California at Los Angeles's Laboratory of Brain, Behavior, and Pharmacology are using an approach called quantitative EEG (QEEG).

Electroencephalography (EEG) uses a cap of electrodes placed at multiple locations across the scalp, each of which measures electrical activity coming from the brain at that particular spot. Neurologists frequently use EEG readouts to diagnose conditions such as epilepsy or brain injury. But instead of using the raw data--a set of jerky, squiggly lines, with each line corresponding to a single electrode--UCLA researchers employ an algorithm that mathematically analyzes data from all of the electrodes to transform the results into a map of brain activity.

The lab is using this quantitative EEG to determine how different individuals' brains respond to different antidepressants, trying to find early markers that indicate whether a new therapy will be effective. But in addition to efficacy, research psychologist Aimee Hunter is also interested in side effects, since those often appear long before any improvement in mood. "And with all the increased press about antidepressants causing suicidal ideation, I began looking for brain changes that might specifically be related to that," says Hunter, who is the lead author of a paper about the research, which was published in the April issue of Acta Psychiatrica Scandinavica.

An earlier study by Hunter and her colleagues, in which healthy volunteers were placed on either placebo or antidepressants, pinpointed the midline-and-right-frontal (MRF) portion of the brain as a region of interest. Those on medication showed moderately decreased activity in this area after just a week, while placebo-takers exhibited a slight increase. Focusing on the MRF region, Hunter then examined QEEGs from 72 adult patients who had been randomly assigned to take either medication or placebo for eight weeks. At multiple time points--48 hours, one week, two weeks, four weeks, and eight weeks after starting their therapy--the patients returned for QEEG measurements and a mood-assessment questionnaire.

When Hunter examined the results, she found a striking effect: Those patients on antidepressants who indicated any increase in suicidal thoughts also showed a drastic decrease in activity in their MRF region just 48 hours after starting their meds--six times the decrease shown in subjects with no change in suicidal thoughts. But after one week, the two groups were nearly identical again.