1. A non-transitory computer-readable medium having computer-executable instructions operable to cause a computer to; receive patient data indicative of a patient's age and sex; receive drug history data that identities drugs taken by the patient; apply one or more drug diagnosis rules to the patient data and the drug history data, the drug diagnosis rules defining relationships between drug history data, the patient's sex, the patient's age, and a diagnosis; and, infer the diagnosis for the patient based on the application of the one or more drug diagnosis rules.