With the expanded and extended use of stimulants comes mounting concern that the drugs might take a toll on the brain over the long run. Indeed, a smattering of recent studies, most of them involving animals, hint that stimulants could alter the structure and function of the brain in ways that may depress mood, boost anxiety and, contrary to their short-term effects, lead to cognitive deficits.
Human studies already indicate the medications can adversely affect areas of the brain that govern growth in children, and some researchers worry that additional harms have yet to be unearthed. Researchers have found that cocaine has remodeled the brains of such ex-users. Similar problems—principally, perhaps, difficulty experiencing joy and excitement in life—could occur after many years of Ritalin or Adderall use.
Amphetamines such as Adderall could alter the mind in other ways. A team led by psychologist Stacy A. Castner of the Yale University School of Medicine has documented long-lasting behavioral oddities, such as hallucinations, and cognitive impairment in rhesus monkeys that received escalating injected doses of amphetamine over either six or 12 weeks.
Compared with monkeys given inactive saline, the drug-treated monkeys displayed deficits in working memory—the short-term buffer that allows us to hold several items in mind—which persisted for at least three years after exposure to the drug. The researchers connected these cognitive problems to a significantly lower level of dopamine activity in the frontal cortex of the drug-treated monkeys as compared with that of the monkeys not given amphetamine.
