Marijuana’s legalization makes for popular politics, but research on weed urges caution. Though it has shown an ability to ease pain and blunt symptoms of several chronic illnesses, ingesting marijuana, like alcohol, can be dangerous for some — and downright dire for teens, children and fetuses.
First, let’s admit there’s a lot to like, beyond those feelings of being lost in a timeless sea of bliss. In more than 100 clinical trials, marijuana has demonstrated its ability to quell pain that no pharmaceutical drug can shut off, including pain rooted in various forms of cancer and the unrelenting pain from damaged nerves. It soothes the nausea that accompanies chemotherapy.
Two chemicals in marijuana — delta-9-tetrahydrocannabinol and cannabidiol, known as THC and CBD, pot’s chief intoxicators — have been shown to work together to slow the growth of cancer tumors, particularly in conjunction with radiation treatments.
A February 2014 report in the Journal of Pharmacology offers evidence that marijuana can relax the suffocating lung contractions of asthma by blocking a biochemical that exacerbates the symptom. Extracts of marijuana, formulated to precise dosages, can control spasms caused by multiple sclerosis, according to the American Academy of Neurology, and are now available by prescription in Germany. In addition, the results of a 2013 Tel Aviv University study reported in the Journal of Neuroimmune Pharmacology indicate that cannabis can guard against the dramatic inflammation that accompanies MS. The Israeli army has permitted soldiers to use marijuana as a treatment for post-traumatic stress disorder and pot’s power to relieve depression is acclaimed by its users, if not yet entirely by research.
The evidence for the herb’s benefits is so strong that US Surgeon General Vivek Murthy said in February 2015 that “we have to use that data to drive policymaking” — and many states are, rushing headlong to full legalization. But at what risk?
Why you get high
Like tobacco and chocolate, marijuana is made up of hundreds of substances that push buttons in the central nervous system and elsewhere in the body, associated with pleasure and relaxation. In the 1980s, researchers set out to discover how marijuana makes you high. They stumbled onto an entire new physiological arena — the “endocannabinoid system” that was named for the plant that inspired the work.
The brain’s biochemistry of pleasure, relaxation and reward involves cells that fit together like a lock and key. When a brain cell wants to send a message to another, it releases molecules of chemicals called neurotransmitters. The catalog of neurotransmitters includes thousands of unique molecules, each with its own shape designed to convey a specific message. A neurotransmitter sails the fluid between brain cells and along the nervous system until it finds the right place to dock and deliver its message. The dock, in this case, is a protein molecule on the membrane of a cell. The molecule is shaped uniquely to receive that specific neurotransmitter, much like a lock is shaped to snugly receive only one shape of key.
It turns out that neuroreceptors for cannabis’ chemical payloads are more numerous than any other receptors in the body, particularly concentrated in areas of the brain related to learning, memory, motor coordination and pleasure. We have them because the body makes neurotransmitters with molecular shapes that mimic those of the happiness compounds in marijuana — now called “endocannabinoids” — that have been found to contribute to various forms of bliss, such as “runner’s high,” the sigh of satisfaction when you eat a warm slice of pie or that post-coital glow.
Science of cravings
New research from the University of California Riverside’s School of Medicine and the University of California Irvine has even explained why grass gives you the munchies. A team led by Dr. Nicholas DiPatrizio found that tasting fatty foods increases the production of endocannabinoids that, the researchers believe, bind to receptors in the small intestine and signal the brain that it’s time to eat more of the same.
In our prehistoric days, finding food was always chancy. So when our ancestors found high-energy foods — things with lots of fats or carbohydrates — the body’s biochemical happiness system rewarded that discovery by releasing endocannabinoid neurotransmitters, leading our foreparents to snarf down as much of that food as they could while it was available. Those biochemical pathways are still with us, explaining why eating one salted peanut makes you want to eat the whole bag. When marijuana’s chemicals circulate through the bloodstream, they eventually land on those gut-level receptors and bind there. That not only triggers signals of hunger from the gut, but also explains why the munchies make you crave a double order of fries instead of a handful of celery sticks.
So if the brain makes its own endocannabinoids, why aren’t we hungry and high all the time? Left to itself, the brain also makes chemicals that regulate the production of these droplets of joy.
Marijuana’s compounds dampen the production of those regulators, not only hampering our ability to turn from bliss to business, but also flooding our brains with chemicals that set off most of our happiness receptors at once.
Luckily, the brain isn’t trapped on this treadmill of artificial joy. Research has found that the dampening effect lasts only until the smoke clears — although some studies indicate that chronic users who quit may go through a brief period of depressed production of internal happiness molecules, making it harder for quitters to experience pleasure or be motivated to seek it outside of a bag of reefer.
Too much of a good thing
Clearly, the brain doesn’t want us to have too much of a good thing — and there’s mounting evidence that marijuana isn’t entirely a good thing after all.
First, your lungs don’t differentiate between smoke from a doobie, a cigarette or a burning building; they all do damage. A report published in June 2013 in the Annals of the American Thoracic Society notes that “Regular smoking of marijuana by itself causes visible and microscopic injury to the large airways that is consistently associated with an increased likelihood of symptoms of chronic bronchitis.”
Pot smoke contains many of the same carcinogens as tobacco vapors and, according to the Foundation for a Drug-Free World, contains up to 70 percent more of them. The foundation cites one study purporting to show that smoking one joint has the same effect on the lungs as smoking five cigarettes one after the other. There’s also anecdotal evidence, and hints from statistical studies, that pot can cause blood clots and even heart attacks in otherwise healthy people.
Various studies point to links between mothers who ingest we
ed regularly while pregnant and babies born smaller in size and lighter in weight. A study of almost 420,000 Australian infants found a greater risk that a newborn will wind up in intensive care if Mom tokes while pregnant. Obstetric-ward nurses have reported indications that infants born to heavy users go through withdrawal, showing irritability, jitters and exaggerated responses to being startled. Also, evidence, though not conclusive, is mounting that children of mothers using pot steadily while pregnant are more subject to chest infections, learning difficulties, poor motor skills, anxiety, depression and various forms of cancer. In January 2014, researchers at Sweden’s Karolinska Institute and the University of Vienna reported findings that THC ingested by pregnant women can interfere with wiring patterns being laid down in a fetus’ cerebral cortex, where memory and learning live.
Fathers aren’t off the hook, either. Some statistical analyses correlate a man’s use of pot in the year prior to their children’s birth with a higher risk of Sudden Infant Death Syndrome in their infants and forms of childhood cancer. A few scientists go so far as to claim that fathers who become addicted to grass at some point in their lives are more likely to have children with personality disorders and behavior problems.
One of the most alarming reports of marijuana’s effects on the brain comes from a 2012 investigation from Duke University and the Institute of Psychiatry at King’s College London. Researchers studied more than 1,000 New Zealanders from their childhood into middle age, focusing on people who began using cannabis by age 18 and continued the habit as adults. The study found that these users lost an average of eight IQ points by age 38. That might not sound like a lot, but dropping from an IQ of 100 — considered baseline average intelligence — to 92 drops you from the 50th percentile of the population to the 29th. People with that level of intelligence have a hard time qualifying for or keeping middle-class jobs. Perhaps the most frightening aspect of the study is evidence that these chronic users didn’t fully regain their lost IQ points even if they quit after 20 years of steady use.
These effects aren’t seen in people who begin going steady with Mary Jane after the age of 20, leading scientists to conclude that cannabis somehow interferes with normal brain development during the teen years. No one is sure of how that might happen, although two theories have been offered.
In adolescence, the brain is still laying down myelin — a blend of fats and proteins that sheath the brain’s neurons. Like the plastic insulation on electrical wiring, myelin keeps the brain’s messages traveling along chosen routes. Some neurobiologists theorize that some of the chemicals in marijuana interfere with this process of “myelinization,” leaving nerve pathways incompletely covered.
Other researchers think that cannabis could interfere with the brain’s streamlining process that occurs prior to adulthood. Children’s brains form countless connections and patterns as they test various ways in which to be in the world. As a child develops and forms habits and a personality, some patterns are used less and less. In adolescence, the brain scraps these idle connections and patterns for the sake of efficiency. If cannabis doesn’t let that happen, then the brain could be left with a maze of connections that lead nowhere useful.
However, not everyone is ready to accept the Duke study’s conclusion. A review published in January 2013 online in the Proceedings of the National Academy of Science offered a smoke-free explanation of the results. Conducted by Ole Rogeberg, a labor economist at Oslo’s Ragnar Frisch Centre for Economic Research, it concluded — as a labor economist might be expected to — that the loss of IQ points was due not to blowing weed but to social and economic inequity. Using simulated data, Rogeberg correlated the same loss of IQ points with the study subjects’ socioeconomic status and concluded that persons’ IQs atrophied due to a lack of education in youth, leading to a lack of intellectual stimulation in adulthood.
Madeline Meier, the Duke study’s chief author, dismisses Rogeberg’s contention. She and her colleagues used actual (not simulated) data to test whether cannabis-associated IQ loss was apparent among individuals from middle-class families. They found that, even among those from comfortable backgrounds, persistent cannabis use was associated with IQ loss.
More bad news: Marijuana may shrink your brain. A November 2014 study from the University of Texas Center for Brain Health made MRI scans of the brains of 48 long-time cannabis users and compared them with scans from 62 non-users, matched to the users’ ages and genders. The analysis found that chronic tokers had smaller orbitofrontal cortexes — a part of the brain holding significant sway over learning and motivation — than abstainers. The results also confirmed the Duke finding that, as a group, people who use marijuana for a long time have lower IQs than those who don’t.
Dr. Francesca Filbey, leader of the Texas team, is quick to point out that their work doesn’t prove that marijuana causes shrunken cortexes or a loss of smarts; it may be that people with naturally smaller orbitofrontal cortexes or lower IQs simply are more inclined to use marijuana. But the group did find two intriguing clues:
— Literature from animal studies indicates that long-term marijuana use is toxic to neurons.
— The group found increased connections among neurons in the cortexes of heavy users — an abnormality in everyone except children.
Filbey theorizes that the increased connections may be the brain’s way of trying to keep functioning normally as tokers’ brain cells die at a higher-than-normal rate. Sadly, after about five years, the brain gives up, and these added connections begin to fade away.