As is any Euphoriant, but as we've seen with drug addition and trafficking in western nations, only hopelessly depressed people consume it and only the elites profit from its sale. Destructive as the Portuguese and British were in producing Heroine for the Asian market, tens of thousands were already consuming Opium despite the culture being fully aware of the risks in its use for several centuries. This suggests that there were already internally organized efforts to destroy Imperial Chinese society which were profiting from the opium/heroine trade.