Cancer has the biopsy, kidney disease has the urine test, and HIV has the cheek swab, yet diagnosis for mental illness is often nothing more than a survey or a conversation with a psychiatrist. A lack of distinct biological markers of disease could be doing huge disservice to patients, says Alexander Niculescu, a psychiatrist and neuroscientist at the Indiana School of Medicine. "If you can demonstrate you're dealing with a biological abnormality just like all the other medical disorders," he says, "you'll not only destigmatize the illness, but also pave the way for better treatment."
Analyzing brain chemistry is notoriously difficult because extracting a tissue sample could have disastrous consequences on cognitive function, and fMRI provides limited information. Blood tests are an attractive option, not just because they're cheap and commonplace, but also because blood can provide useful indications of brain state. (For more on biological testing, see To Know or Not to Know)
Though the field is progressing rapidly, some experts caution against prematurely jumping onto the bandwagon. "It's too early to be directly marketing blood-based expression tests to consumers," says Stephen J. Glatt, a psychiatrist at SUNY Upstate Medical College. At this stage of development, blood tests, he stresses, would only offer false hope and false certainty. Still, there is a demonstrable biological connection between brain and blood, Glatt adds: "Be hopeful, but be skeptical and patient." Here's a snapshot of progress in the field. —Tarah Knaresboro