Drug tolerance is contextual. It can vary, depending on the external environment and even the thoughts of the user. The key idea is that tolerance-related drug potency increases in unfamilar environments or mental states.
There is much research that bears this out, with experiments going back to at least 1975. Overdoses are even thought to have occurred as a result. This suggests that tolerance often has a strong element of learning, despite what many students in my substance abuse classes inititally think. You should see their faces.
This obviously has implications for addiction, as the higher the tolerance to an addictive drug, the lower the pleasure of using, but the more severe the negative consequences for abstaining. And of course, many seemingly hold the idea that familiar environments in which drug use occurs tempt addicted users. Hence, the encouragement given to many substance abuse patients is to avoid such environments, along with changing some of the ways they think about their addictions and any related problems. Perhaps the danger of patients using in novel contexts with increased enjoyment is often overlooked as a risk for relapse.
Any "highs" addicted users enjoy are not the only experiential aspects that suffer tolerance. There are many other physiological effects that are also context-dependent. For example, take the antinociceptive(pain relief) effects of opiates.
Interestingly, there is a flip side of learned tolerance. This involves the use of cues for drug consumption to elicit feelings of intoxication. There are many experiments in which participants are given alcohol placebos and report and otherwise display evidence of intoxication. There is also a humorous video here.
Finally, I offer a hypothesis. Since learned drug tolerance fails to transfer to the degree that a context is novel, it should hence diminish during laughter. Given that laughter involves gain/loss-independent expectancy violations, this would seem a safe bet(1). I'm still looking for a study to address this question. If any of you find one, please let me know.
1. Nerhardt, G. Humor and inclinations of humor: Emotional reactions to stimuli of different divergence from a range of expectancy. Scandinavian Journal of Psychology. 1970, 11, 185-195.
Quantitative Psychological Theory and Musings