Psychiatrists make life-altering decisions on the basis of a subjective assessment of a set of symptoms. But many freely admit they have far too little information to answer some critical questions: Is the patient suffering from severe depression, or is this a case of bipolar disorder that hasn’t fully manifested itself yet? Will this schizophrenic patient respond to this drug? Draw the wrong conclusions about a depressed patient and the treatment may send him careening into mania. Make the wrong assessment of a schizophrenic person and you may give him an ineffective drug whose side effects could kill him.