The 1936 film Reefer Madness developed a cult following because of its over-the-top depiction of the evils of marijuana. Getting stoned and going to a midnight showing became a ritual for many college students.

The recognition that pot is not a direct route to an asylum for the criminally insane, as it was for one character in the film, fueled the hilarity for late-night moviegoers. The divergence between perception and reality has become an issue in recent years for other recreational drugs.

Last month four scientists from Columbia University published an analysis of previous studies on methamphetamine use that called into question some of the purported damaging effects of the drug on brain functioning. The review in Neuropsychopharmacology found that short-term effects of the drug actually improve attention, as well as visual and spatial perception, among other things.

Moreover, chronic users—the ones who would be expected to suffer most—remain largely unimpaired. The researchers found that they experience brain and cognitive changes “on a minority of measures” in brain imaging and psychological tests. “Cognitive functioning overwhelmingly falls within the normal range,” the report states, while adding that researchers’ pre-existing assumptions about meth's detrimental effects "should be reevaluated to document the actual pattern of cognitive effects caused by the drug."

While recognizing the potential for abuse, the researchers emphasize that misinterpretations of the scientific evidence can wrongly stigmatize drug abusers and lead to misguided policymaking. One study, for instance, asserted that meth abusers might be too cognitively damaged to benefit from rehabilitative treatments, such as cognitive behavioral therapies. “Findings from this review argue that such concerns are unwarranted,” the researchers state.

In Thailand, efforts to stem meth use have gone as far as banning all amphetamines, a class of drug that is used medically for treatment of ADHD and other conditions. “My main goal really was to make sure that we are rigorous in the science before we are political,” says Carl Hart, a substance abuse researcher at Columbia who was the lead author on the Neuropsychopharmacology paper. “I think, with meth, we have been political.” (Neuropsychopharmacology is part of Nature Publishing Group, which also includes Scientific American.)

The article asserts that some of the misconceptions surrounding meth go beyond findings on mental functioning. Drug education campaigns often publish photographs of “meth mouth,” severe tooth decay among users because of the lack of saliva. But dry mouth is a condition common to other drugs, such as the prescription antidepressant Cymbalta and the ADHD medication Adderall.

Hart says he was impelled to do the research because of distortions of the evidence for harm from crack cocaine. During the crack cocaine epidemic in the 1980s and 1990s, pronouncements about lasting prenatal harm to children whose mothers used the drug turned out to be overblown: long-term effects on brain development and behavior were fairly small, and children were sometimes ostracized or received medical diagnoses that were mistakenly attributed to effects from the drug.

The review by Hart and colleagues elicited a firm counterpoint from National Institute on Drug Abuse director Nora Volkow, some of whose research is critiqued in the Neuropsychopharmacology paper. “Because of the far-reaching public health implications of this issue, it is essential not to forget what we do know about meth-induced neuropathology, which is plenty troubling,” she says. Volkow points out that the vascular effects of meth can lead to strokes and hemorrhages. The drug, she notes, has also been shown to produce inflammation, atrophy and structural changes in brain tissue. “Similarly worrisome is a recent report of increased incidence of Parkinson’s diseases among individuals with a past history of methamphetamine abuse [compared with] the general population,” she says, adding that meth abuse can be “neurotoxic to the human brain.”

Hart responds that he and his colleagues were careful to consider the full body of scientific literature, including animal studies. He points out that many animal studies used to extrapolate possible deleterious cognitive effects in humans had administered large amounts of methamphetamine from the outset, a regimen unlike the gradual escalation in dosing undertaken by illicit drug users, which avoids these consequences. The article emphasizes that serious medical consequences, such as paranoia and hypertension leading to stroke, are rare and only result from sustained ingestion of very large doses.

Meth’s persistent bad boy reputation means that medical marijuana dispensaries will not be expanding their offerings to include speed any time soon. Still, the idea is not as totally outlandish as it might seem.

A much cited commentary that appeared in Nature in December 2008—an article co-authored by neuroscientists and ethicists—raised the prospect of routine use of “cognitive enhancement” drugs by the general public if they could be proved safe.

The few drugs already on the market that come closest to meeting the definition of cognitive enhancers include Adderall (dextroamphetamine and amphetamine) and Ritalin (methylphenidate), close chemical cousins of methamphetamine. Ritalin and Adderall, in fact, have developed a reputation as executive’s little helpers in the business world and were cited in the Nature commentary.

Hart and his colleagues never suggested that methamphetamine could serve as a pick-me-up for meeting pending work deadlines. Their review, though, looked at more than 10 studies that found that short-term use of meth actually improves several cognitive measures, precisely the kind of evidence the authors of the Nature article were calling for when considering the merits of enhancement.