On the Road with Rick Holmes: As laws change, scientists rush to unlock the promise and peril of marijuana

The implications of what we’re learning about what cannabis does to the brain are profound, but there is still a lot we don’t know. As researchers often say, more research is needed.

By Rick Holmes 
 
Belmont, Mass. – McLean Hospital looks more like another college campus nestled in the Boston suburbs than a mental institution. But since 1818, McLean, originally called an “Asylum for the Insane,” has provided the best mental health treatment its patients – or their insurance companies – can buy, delivered by top psychiatrists.

McLean’s is a respected research center as well. Among other things, it’s one of the few places in the world where scientists can watch people’s brains as they smoke weed. Using brain imaging machines, they’ve seen your brain on drugs, and no, it doesn’t look like an egg sizzling in a frying pan.

What researchers like Staci Gruber, director of McLean’s Cognitive and Clinical Neuroimaging Core, are discovering about marijuana, could hardly be more urgent. Medical marijuana is now legal in 29 states, recreational marijuana is legal in six states and counting. In response to a growing market, marijuana itself is changing, with new cannabis products, new ways of consuming them, new strains stressing different cannabinoids and ever higher potency.

As always, science on what marijuana does to you, or can do for you, is way behind the politics.

Gruber and other brain researchers are rushing to catch up.

One of Gruber’s findings is that the brains of those who begin using cannabis regularly before age 16 are undeveloped. “The brain grows from back to front, and bottom to top,” she told me, and the last to develop is the frontal cortex, which is responsible for higher cognitive functions like focus and impulse control. Up to the mid-20s, that part of the brain is still developing, and heavy, chronic use of cannabis disrupts that growth. You can see it, she explains, in the way their “white matter” appears on brain scans, and in how they handle cognitive tasks.

Do adolescent potheads catch up in their brain development later in life? We don’t know, Gruber says, because we haven’t done the long-term studies. Nor do we know the effect of new strains and higher potency concentrates on the adolescent brain. But we do know that the age of first marijuana use is getting lower. We also know, she says, that the brains of those who take up cannabis as adults appear no different from those of people who never tried it.

With adult cannabis use increasingly accepted, the way we explain the danger to children is critical.

“Just say no” isn’t very effective at changing teen behavior, Gruber says, but “Just not yet,” and “it’s worth the wait” have more success.

The other thing that scientists are learning is that medical marijuana really works.

After considering more than 10,000 research abstracts, The National Academies of Sciences concluded in January that cannabis has therapeutic benefits in treating muscular spasms related to multiple sclerosis, side effects from cancer chemotherapy and chronic pain in adults. That last, chronic pain, is relevant to a drug crisis more serious than reefer madness has ever been: the epidemic of opioid addiction.

Here at McLean, a study of adults first introduced to cannabis through medical marijuana treatment found dramatic improvements in the same cognitive functions that suffer when adolescents use recreational pot. They report they are better able to concentrate and keep an even keel. They sleep better, feel healthier and cut back on the use of other medications. One especially dramatic finding: a 42 percent reduction in opioid use once they started using medical marijuana.

It’s too soon to say whether cannabis can be used to treat addiction, but there is growing evidence that it can be an effective alternative to the prescription painkillers that have done so much to fuel the current epidemic. That’s new science every drug policy-maker should absorb.

Cannabis is a most complicated plant, Gruber explains. The parts of it that make people high, mainly the cannabinoid THC, can also make users paranoid and slow frontal cortex development. But other components, including the cannabinoid known as CBD, reduce pain and anxiety, and may help protect or even repair the frontal cortex.

The implications of what we’re learning about what cannabis does to the brain are profound, but there is still a lot we don’t know. As researchers often say, more research is needed.

Meanwhile, botanists working for legal marijuana dispensaries, and chemists working for pharmaceutical giants, are inventing new strains of cannabis and isolating its component parts.

THC levels are being raised to please the recreational marijuana market, and average CBD concentrations are going down. They are putting these new products into edibles, salves, tinctures, and pre-loaded vaporizer pens, with a dizzying variety of strains. Physicians and patients using this new medicine must make it up as they go along, with little research-based guidance on dosages or therapeutic methods.

It’s a crazy way to implement a medical discovery, but it’s no surprise.

For 100 years America has put politics and profits ahead of science when it comes to drug policy.

That blinds us still to both the perils and promise of marijuana.