The term narcotizing dysfunction was coined in the 1950s by Paul F. Lazarsfield, who studied the influence of media by designing a study to determine how media influenced voters' choices. During his study, he discovered that when people learn information from radio or other media sources, people will not consequentially respond to this information. Since information learned from media does not necessarily generate a response, information actually does not influence voting decisions. Instead, he learned that people greatly rely on who he dubbed "opinion leaders" to make actual voting decisions to act upon. But most surprising is that "an opinion leader could be just about anyone, from a homemaker next door to a coworker on the assembly line" (New World Encyclopedia, "Paul Lazarsfeld"). In addition, these opinion leaders themselves were significantly informed through various forms of media.
One of the most important conclusions he reached based on his study is that information from the media does not lead the majority of people to take action; it leads to "apathy or inertia" ("Paul Lazarsfeld"). In fact, being "bombarded with more and more information" leads only to "the public's increasing apathy or inertia." Only a few "opinion leaders" are not led to apathy, and those few have the power to exploit the rest of the public, as evidenced by the Nazi's use of propaganda during World War II ("Paul Lazarsfeld").
Hence, the harm of narcotizing dysfunction is that it leads to apathy and even brainwashing.