No prólogo do SdA, Tolkien se refere ao tabagismo:
There is another astonishing thing about Hobbits of old that must be mentioned, an astonishing habit: they imbibed or inhaled, through pipes of clay or wood, the smoke of the burning leaves of a herb, which they called pipe-weed or leaf, a variety probably of Nicotiana.
O próprio Tolkien foi um fumante de cachimbo durante toda a sua vida, e se referiu a ele na Carta 294 nestes termos:
I should forgo smoking on these occasions, but I have found being interviewed increasingly distasteful and distracting, and need some sedative.
(minha ênfase)Em relação às propriedades semelhantes às drogas observadas, seria útil notar que a nicotina em si é uma droga altamente viciante com efeitos psicoativos. Se posso citar o artigo da Wikipedia :
When a cigarette is smoked, nicotine-rich blood passes from the lungs to the brain within seven seconds and immediately stimulates the release of many chemical messengers such as acetylcholine, norepinephrine, epinephrine, vasopressin, histamine, arginine, serotonin, dopamine, autocrine agents, and beta-endorphin. This release of neurotransmitters and hormones is responsible for most of nicotine's effects. Nicotine appears to enhance concentration and memory due to the increase of acetylcholine. It also appears to enhance alertness due to the increases of acetylcholine and norepinephrine. Arousal is increased by the increase of norepinephrine. Pain is reduced by the increases of acetylcholine and beta-endorphin. Anxiety is reduced by the increase of beta-endorphin. Nicotine also extends the duration of positive effects of dopamine and increases sensitivity in brain reward systems.
Não parece haver necessidade de complicar as coisas procurando outras explicações. A nicotina sozinha é suficiente.