This has just reminded me of something I was taught in a summer class last year, it was a psychology course and we were taught about how the brain associates with certain environments when drug taking. For an example, if a drug user always takes his/her hits, in a bathroom, the brain associates the drug taking with being in the bathroom and as the tolerance grows so does this association but then for one reason or another, the drug taker takes drugs in a different environment, for example, the park, the brain doesn't recognise this environment associated with the drugs and acts completely differently, metabolising the drug in a completely different way and without the built up tolerance.
We were told that this situation accounts for many OD deaths in long term users.
Environment Contributes To Drug Tolerance - ScienceDaily
"If the same amount of a drug is administered in one context and later in another different and distinct context, then the effects of the drug are different," Cepeda-Benito says.
"The drug has a much greater effect in a novel context rather than in a context that is associated with the administered drug."
Cepeda-Benito, who has studied morphine and nicotine's effects, terms this phenomenon "learned tolerance," and says gradual desensitization to a drug can be developed not only by repeated use of the drug, but also through a learning process that involves recognizing the environment.
In other words, a person consuming a drug in a setting where he or she usually consumes the drug or even expects to consume it will be less likely to feel the full effects of the drug, he says.
However, if that same person takes the same amount of the drug in a setting where he or she doesn't normally take the drug, then the person is likely to feel a greater effect from the drug."
