Excerpt from
Tastes of paradise: a social history of spices, stimulants and intoxicants, by W. Schivelbusch:
"The East India Co had enjoyed a lively trade relationship with with Chinese Empire ever since the 17th century. The various chinoiseries that were all the rage among the European upper classes--tea, silk, porcelain--represented lucrative items of trade. In the 17th and early 18th century, when the Middle Empire was still an equal partner of the European powers, these articles were regularly paid for in cash, because the Chinese had no use for anything the Europeans could offer them in exchange.
However, the situation changed during the 18th century when the Chinese Empire grew proportionately weaker as the European powers, above all England, became more and more agressive. Trade between equal partners was transformed into a trade dictatorship by the East India Co, which enforced its will by means of its own militia. Instead of continuing to pay for Chinese products in cash, the company now offered a special trade item, opium. It was a cheap commodity for the company, produced on a large scale on its plantations in India. Estimates are that between 1767 and 1850, in less than a century, Chinese opium consumption increased 70-fold. Obviously, such an increase brought far-reaching social consequences. The comparision with the English gin epidemic springs to mind. One might also compare the role opium played in China since the 18th century with that of coffee in Europe since the 17th century: the stagnation of sociopolitical life in China, one might say, was reflected in opium consumption, just as the early capitalist activity of Western Europe was reflected in its coffee consumption.
It is astounding how deliberately and systematically the colonial masters were able to deploy opium to this end. They took it for granted, of course, that this commodity was to be used only outside their homeland. The East India Co itself, the instigator and chief beneficiary of the opium trade, declared in a statement of 1813 how repugnant a thing it considered opium."