Complex sentence: The World Health Organization (WHO) classified it in 1980 as a drug of abuse that can produce psychological dependence, although the WHO does not consider khat addiction to be seriously problematic.
Split into simpler sentences: The World Health Organization (WHO) classified it as a drug of abuse. In 1980, the World Health Organization (WHO) classified it as a drug of abuse that can produce psychological dependence, although the WHO does not consider khat addiction to be seriously problematic.