Previous estimates had suggested that IED could be found in approximately 2.7 percent of the general population, but many experts believe it may be much more common and that it may be an underrecognized cause of much violent behavior. One study from the National Institute of Mental Health (NIMH) suggested that, broadly defined, IED may actually affect as many as 7.3 percent of adults, or as many as 16 million Americans. Those with persistent and more destructive recurring episodes of IED may have, on average, 43 such attacks over the course of a lifetime.