Legalize Marijuana? Obama Was Right to Say No

Pot is bad for the brain, especially young brains.

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By Bernadine Healy, M.D.

Puff the Magic Dragon—in his naughtier incarnation—bit the dust when President Barack Obama recently made it clear that he is against legalizing marijuana. His message was delivered on his website,, even before he placed his hand on the Lincoln Bible. Astonishingly, legalization of marijuana ranked as Priority No. 1 for the new administration among the thousands of possible actions voted upon on the website by the public. Yes, even above stem cell research, the war in Iraq, and Wall Street bailouts. Obama's prompt no to the query "Will you consider legalizing marijuana so that the government can regulate it, tax it, put age limits on it, and create millions of new jobs and create a billion-dollar industry right here in the U.S.?" dashed the hopes of many who thought our young, hip, new president—who long ago dabbled in the stuff and, by his own admission, inhaled—would come to marijuana's rescue.

Listen to the president's inauguration speech, and it seems clear why he's unwilling. In a "new era of responsibility," somehow a fat new billion-dollar U.S. marijuana industry doesn't quite square with a world that almost universally outlaws the stuff. Making weed as accessible to our children as cigarettes doesn't fit with Obama's words to parents about nurturing their children, as he and Michelle so sweetly do their own little girls. And it would be the antithesis of the inaugural pledge he made to respect science.

Scientific research from the National Institute on Drug Abuse and elsewhere leaves little doubt that marijuana abuse is bad for brains, particularly younger ones. The psychoactive chemical in weed, THC (short for delta-9-tetrahydrocannabinol), binds to a class of receptors known as cannabinoids that are dense on neurons in brain areas associated with thinking, memory, concentration, sensation, time perception, and emotions like fear, anxiety, and pleasure. Once THC has delivered its buzz, it hangs around for days, if not many weeks, accumulating with regular use. The lingering chemical makes drug testing possible long after the last puff, and it also means that weekend joints carry a low-grade marijuana haze into the next week, perhaps contributing to marijuana's so-called amotivational syndrome.

Researchers remain unsure whether the residual effects of cannabis on intellectual performance, attention span, and learning ability now identified in users (including college students) represent lingering drug, withdrawal symptoms, or toxic damage. Evidence is accumulating, however, that heavy drug use is associated with lasting damage. Just published in the journal Pediatrics is a prelimnary study of young men who had been heavy marijuana users starting in their early teens. MRI scans showed disrupted neural development in the brain areas that influence memory, attention, and high level decision making, areas known to develop and mature during adolescence.

As for marijuana's association with anxiety, depression, and suicidal or even psychotic thinking, it's hard to say whether the mental disturbances are caused by the drug or are the trigger for its use in those already struggling with a mental illness. But however it's argued, academic stars are rarely potheads, and regular exposure to this powerful psychoactive drug is a nasty idea for developing young minds trying to study hard, mature emotionally, and get started in life.

Moreover, contrary to popular thought, NIDA stresses that marijuana can be physiologically and psychologically addictive. And Australian scientists recently reported that cannabis junkies hooked for more than 10 years develop brain injury. Compared with matched controls, users in this relatively small but provocative study scored lower on mental health and cognitive performance measures, and their MRI scans showed brain shrinkage in regions targeted by cannabis. Face it: Were the crude, dried, ground weed reviewed by the Food and Drug Administration for safety, it would flunk on its brain effects alone.

Yet cannabis has adverse effects on more than the brain. The heart is stressed by marijuana, which for one thing elevates serum triglycerides that bring coronary disease risk. Marijuana is a serious respiratory irritant that serves up more carcinogenic hydrocarbons than tobacco smoke. When pregnant women smoke, the drug gets into the fetus; in nursing mothers, it enters breast milk. And in the cannabis-receptor-laden testicles, there is growing evidence from the laboratory and in humans that THC causes mutant sperm, which among other things can't swim right—thus impairing male fertility, at least while the male and his sperm are under the influence.

Clearly, legalization of medical marijuana use is a more persuasive battle cry than that of recreational highs. The FDA has already approved synthetic THC in pill and suppository form to stimulate appetite (the marijuana "munchies") and to ease the nausea of chemotherapy in seriously ill or terminal patients. Anti-inflammatory and pain-perception benefits may be important as well.

That said, the science remains immature and stymied by ideological and moral objections, at a time when there is much to be learned both about a drug that's so commonly used and about the body's own natural and still-mysterious cannabinoid receptor network. In the spirit of honoring science and an open mind, such work should be pursued—and, I might add, compassion and consideration afforded the sick and dying who use marijuana under a doctor's care.

As for the rest of society, arguments for legalization will rage: End the criminal underground that prohibition fosters; let adults be free to grow and smoke whatever they wish; or, lamely, pot's no worse than other—legal—vices. But as I see it, in an age of responsibility, protecting our young people's health is the stronger imperative and should rightfully keep policymakers from cozying up to this brain-toxic drug.

Curious about what teenagers want to know about pot? Read answers to 10 questions kids have about marijuana (and six about alcohol).