In short, drug use temporarily changes the brain’s internal environment: the “high” is produced by means of a rapid chemical shift. There are also long-term consequences: chronic drug use remodels the brain’s chemical structure, its anatomy, and its physiological functioning. It even alters the way the genes act in the nuclei of brain cells. “Among the most insidious consequences to drugs of abuse is the vulnerability to craving and relapse after many weeks or years of abstinence,” says a review of addiction neurobiology in a psychiatric journal. “The enduring nature of this behavioral
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