And scientists still don't know the role of these genes in suicidal thinking, or, for that matter, whether suicidal ideation is a predictor of suicide attempts or actual suicide.
"This research doesn't tell us the mechanism by which treatment-emergent suicidal ideation happens, it doesn't tell us if there's an increase for suicide itself. But these are important questions that we are very interested in following up."
Hype and Hope
Follow-up might come from an independent company called Neuromark -- which jumped on the anticipated publicity from the publication to announce that it has already licensed the agency's patents on the two markers, plus a couple of additional markers that NIMH researchers have not yet published (more on that below), and will immediately begin offering a test for them to physicians. In its press statement, the company also invited "physicians and patients across the country to participate in prospectively collecting data to confirm and extend the predicted risk of the Mark-C test."
A couple of other things would strengthen these findings. One would be discovering the function of the genes flagged by these markers.
"These two genes are involved in the [neurotransmitter] glutamate pathway , and we know that the glutamate pathways have been associated with antidepressant outcomes," says Laje. "So we have seen a link between glutamate and depression and the treatment of depression. [But] we don't know exactly what these changes actually do in the cell yet. We're working on that."
And since 41 percent of patients with treatment emergent suicidal thinking lacked either of the two published markers, there must be other genes, or environmental factors, involved.
In fact, Lajes says his team has already discovered and patented a couple of as-yet unpublished markers. "We will be presenting some additional findings where we linked two other genes to treatment emergent suicidal ideation, and these genes taken together give us a more specific and sensitive way to test for risk for developing this unusual but serious side effect," he says.
The STAR*D study also revealed that the drug was much less effective for patients who had treatment emergent suicidal ideation. So, says Laje, the work could eventually help predict which antidepressant will work best for individual patients.
"We're a step closer to being able to tell who is at a higher risk of developing suicidal ideas when they're taking antidepressants, as well as a step closer to knowing who will respond to an antidepressant, " he says.
"A test might be around the corner, if you will, but we still need to look further into these results to make sure that the phenomenon that we're describing is actually related to the genes that that we found."
This research will be published in The American Journal of Psychiatry, October 2007, and is funded by the National Institute of Mental Health (NIMH) of the National Institutes of Health (NIH).