Review Questions Warnings About Meth's Mental Effects

Doctors prescribe methamphetamine and similar stimulants to improve alertness, attention, and mental acuity. Yet anti-drug propaganda (see above) warns that meth, when consumed without a prescription, impairs thinking and ravages the brain, leading to irrational, disordered, self-destructive, and possibly violent behavior. Does a slip of paper from an M.D. magically transform the properties of this chemical? Or should the warnings about meth-related cognitive impairment be taken with a shaker full of salt? 

The latter, suggests a new research review published by Neuropsychopharmacology. Columbia University psychologist Carl L. Hart and three co-authors report that laboratory experiments generally "show that short-term, acute methamphetamine [consumption] improves cognitive performance of both methamphetamine abusers and non-users in some domains, for example, visuospatial perception, sustained attention, and response speed, even when larger intranasal and intravenous doses are tested." As for long-term effects, "statistically significant differences between methamphetamine users and control participants have been observed on a minority of measures" in studies using brain imaging and cognitive tests. But Hart et al. caution that "the clinical significance of these findings may be limited because cognitive functioning overwhelmingly falls within the normal range." Despite a lack of evidence regarding the practical significance of these results, "researchers frequently interpreted any brain differences as indicative of cognitive pathologies caused by the abuse of methamphetamine." Indeed, "many researchers in this area begin with the assumption that methamphetamine abusers exhibit cognitive dysfunction, and that their research bears this out." Noting that methamphetamine offenses are punished especially severely, partly because of the stimulant's allegedly devastating impact on the brain, Hart and his colleagues caution against repeating the errors that led to draconian crack cocaine penalties, based on misconceptions about that drug's purportedly unique hazards:

This prevailing assumption [that meth causes brain damage] has provided the fuel for a growing number of neuroimaging studies assessing the impact of prenatal methamphetamine exposure. Hopefully, more caution will be exercised when interpreting these findings than was exercised when results were interpreted from studies of infants prenatally exposed to cocaine, who were erroneously and too readily condemned to a life of learning disabilities, psychological disturbances, and crime….

It is only recently that penalties associatedwith crack cocaine violations were reduced. This change came after nearly 25 years of criticism of the law because it was inconsistent with the scientific evidence and it exaggerated the harms associated with crack cocaine use. The monetary and human costs of this misunderstanding are incalculable….

Many of the claims about methamphetamine-associated cognitive impairments are reminiscent of statements made about crack cocaine more than two decades ago before the empirical evidence was clear. Taken together, these observations lead us to speculate whether we are headed down this path once again.

Six years ago in Reason, I noted nascent alarm about "meth babies." In a 2005 column, I highlighted over-the-top warnings about meth.