I think that more psychoactive substances should be added into the game, similar to alcohol. For examples, including some ideas suggested by others in the thread:
Drugs:
Coffee and tea, once made brewable, could contain caffeine which would have mental effects on your dwarves in a similar way to alcohol, as well as delaying tiredness with a crash later or something like that.
Fantasy substances like something analogous to the substance smoked by the h******s in The L**d of the R***s, etc., witches' brews, various psychoactive potions, etc. Potions have probably been suggested elsewhere.
Drugs like opium or hashish or marijuana, things that have a relatively long history of use and would fit in the historical setting. Think like hazy opium dens as an alternative to taverns in a human city where you can find knowledgeable people, quest objectives, etc.
Animal person tribe shamans etc. or maybe even elves could use/administer magical potions/substances or things like peyote, mescaline, psilocybin, ergot (à la the hypothetical kykeon of the Eleusinian mysteries), etc. for their rituals and ceremonies. Taking these could cause hallucinations or connections to the spirit world, etc. depending on the specific case.
Hormones:
Adrenaline should be released from the kidneys in appropriate situations, which would make dwarves or adventurers react differently after being surprised/ambushed, or a mother sees her child in danger, etc. And having impaired kidneys could affect this.
Pheromones:
Substances emitted by creatures that can influence other creatures. This might also include exopheromones, pheromones that can influence across different species. Although it is a bit tricky to think of in-game-viable examples. Perhaps as a mediator of lust?