Drug-Induced Diseases. From Worst.Pills.org.How  Extensive Is the Problem of Specific Adverse Drug Reactions? Each year, more than 9.6 million adverse drug reactions occur in older Americans. One study found that 37 percent of adverse reactions in the elderly were not reported to the doctor, presumably because patients did not realize the reactions were due to the drug. This is not too surprising considering that most doctors admitted they did not explain possible adverse effects to their patients.  [ See full text ]