Marijuana use is on the rise in the U.S., with more than 17 million Americans saying they have used the drug in the past month, according to data from the National Institute on Drug Abuse (NIDA). Two states — Washington and Colorado — have voted to make it legal for adults.
The growing popularity of pot raises questions: Is pot healthy? Does it have benefits? Is it dangerous? The answers, according to experts, is that while marijuana may have specific benefits for certain people it poses serious health risks for many others — especially for those who develop the habit early. The Drug Abuse Warning Network (DAWN), a system for monitoring the health impact of drugs, estimated that in 2009 marijuana was a contributing factor in over 376,000 trips to emergency rooms in the United States, and about two-thirds of patients were male.
The Longterm Risks of an Early Pot Habit
How much you smoke, how often, and whether you combine it with alcohol or other substances affects marijuana’s health consequences. But increasingly, doctors are discovering that another important factor is how early you start smoking marijuana — particularly before age 25, when your brain is still developing. “The brain in development is like lines of code being written in a computer program that will run all future behaviors,” says Ruben Baler, Ph.D., Health Scientist with NIDA. “Using marijuana is like scrambling the letters in your keyboard; the glitches in the program will be sustained for a very long time, because you’re screwing up the actual programming of that routine. If you use marijuana later in life, it’s like scrambling the keyboard after the program has been written; you may have some temporary glitches, but the problems aren’t necessarily long-lasting.”
Using marijuana, particularly in your teens and early 20s can affect your memory and your ability to learn. The primary psychoactive (mind-altering) chemical in marijuana is delta-9-tetrahydrocannabinol (THC). When you smoke marijuana, THC passes from your lungs into your bloodstream and travels up to your brain, where it can distort your perceptions, affect your coordination, and disrupt your learning and memory areas, impairing your ability to think, remember, and solve problems. In chronic users, these effects can be long-lasting, according to the National Alliance on Mental Illness (NAMI). One large prospective study showed that people who began smoking marijuana heavily in their teens lost as much as eight points in IQ between ages 13 and 38; even people who quit smoking pot as adults never regained those lost cognitive abilities.
Other studies indicate that smoking marijuana can raise your risk for depression, anxiety, and suicidal thoughts. “Young people who smoke marijuana also have a higher rate of developing a psychotic illness later in life,” says Ken Duckworth, M.D., medical director of NAMI. “This has been an underappreciated point in the medical marijuana debate. It is unclear whether marijuana causes the psychosis or triggers it in somebody who already has an underlying predisposition, but smoking marijuana potentially causes irreversible harm to the brain, especially in people who smoke it before age 25.”
Adult Risks: Heart Attacks, Stroke, Testicular Cancer, Addiction
If you’re older than 25, you may be more concerned about how marijuana use affects your risk of chronic illness. Here’s what we know:
- Cardiovascular disease Right after you smoke marijuana your heart rate rises by as much as 100 percent and stays elevated for up to three hours. That can lead to palpitations and irregular heart rhythms. The risk is significant: In the first hour after you smoke marijuana, heart attack risk more than quadruples, according to some research. Smoking marijuana doubles your risk of stroke, too, according to a 2013 study from New Zealand.
- Testicular cancer Several studies have shown a link between smoking pot and an increased risk for testicular cancer. In one study, doctors at the University of Southern California found that men who smoked pot doubled their risk for a particularly aggressive form of testicular cancer.
- Fertility problems Smoking marijuana affects the levels of the male hormone testosterone in your body and decreases sperm quality, reducing the ability of sperm to move quickly and increasing abnormalities. In women, pot smoking can disrupt normal menstrual cycles.
- Addiction About 4.5 million people in the U.S. meet clinical criteria for marijuana abuse or dependence, according to NIDA.
Does Marijuana Offer Health Benefits?
In some circumstances, marijuana may confer health benefits, or contain ingredients that can be used therapeutically:
- Type 2 diabetes Researchers at the University of Nebraska and Harvard Medical School recently analyzed data from a large nationwide survey and found an association between smoking pot and reduced risk for developing diabetes. The pot smokers seemed to process insulin more efficiently than non-smokers. More study is needed to understand and replicate this finding and until then, no one should smoke pot to reduce diabetes risk, stress the researchers.
- Nausea treatment This is the most well-known of pot’s benefits, and a major reason why medical marijuana is legal in 18 states. THC is approved by the Food and Drug Administration (FDA), having been shown in controlled clinical trials to relieve nausea caused by cancer chemotherapy and stimulate appetite in people who have AIDS.
- Multiple Sclerosis Sativex, a drug that contains active ingredients from the marijuana plant, is available in Canada and several European countries for reducing spasticity in people who have multiple sclerosis. Sativex has not yet received FDA approval for sale in the U.S.
While marijuana may have some medical benefits, notes Dr. Baler, they are best delivered in a pill rather than a joint. “These medicines deliver these drugs in purified forms and consistent doses,” says Dr. Baler. “You can’t measure exactly how much THC you are getting by smoking a marijuana cigarette. The FDA will not approve marijuana in a smoked form as a medication. The potential benefits do not outweigh the risks.”
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Laura Flynn McCarthy is a New Hampshire-based writer who specializes in health and parenting topics.