Complex sentence: Previously, physical dependence on benzodiazepines was largely thought to occur only in people on high-therapeutic-dose ranges and low-or normal-dose dependence was not suspected until the 1970s; and it was not until the early 1980s that it was confirmed.
Split into simpler sentences: Previously, physical dependence on benzodiazepines was largely thought to occur only in people on high-therapeutic-dose ranges. Low-or normal-dose dependence was not suspected until the 1970s, and it was not until the early 1980s that it was confirmed.