This started as a plot bunny that is unlikely to go any further:
Of course, the day did come when chocolate was found to be as addictive and narcotic as morphine and so classified as an illegal drug in exactly the same way. This was only two weeks after cannabis was reclassified as a medicine and tobacco was shown to be and notified as a dangerous and addictive illegal drug. People's view of these changes must have been similar, I imagine, to when mercury was found to be toxic and both men and women of the wealthier classes had to stop using it to whiten their faces merely for the sake of appearance.
creative 