Diagnosing mental illness isn't like diagnosing other chronic diseases. Heart disease is identified with the help of blood tests and electrocardiograms. Diabetes is diagnosed by measuring blood glucose levels. But classifying mental illness is a more subjective endeavor. No blood test exists for depression; no X-ray can identify a child at risk of developing bipolar disorder. At least, not yet.
Thanks to new tools in genetics and neuroimaging, scientists are making progress toward deciphering details of the underlying biology of mental disorders. Yet experts disagree on how far we can push this biological model. Are mental illnesses simply physical diseases that happen to strike the brain? Or do these disorders belong to a class all their own?
