Tolerance and dependence The more often a drug is used, the more accustomed the brain becomes to its effects. This is called neuroadaption. The common effect of neuroadaption is an increased tolerance to the drug. A person can be said to have developed a tolerance to a drug when: the same dose of the drug no longer produces the effect that it used to increased doses of the drug are needed to get the same effect Tolerance becomes known as dependence when not having the drug begins to produce a negative response: the user needs to take the drug to feel ‘normal’ rather than to get the effect they first began taking the drug for.