Stimulants, because of their direct effects on dopamine, seem to produce far more severe sensitization of wanting and diminution of liking; opioids, because they act on opioid receptors that directly mediate liking, create a less extreme dissociation between the two. And this is why “stimulant maintenance” treatment like using Ritalin to treat cocaine or methamphetamine addiction does not seem to be as successful as opioid maintenance. It is much harder to create tolerance with a drug that imitates the pleasures of desire than it is with one that simulates the experience of satisfaction. While
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