Worldwide, marijuana is the most common illegally used substance. In the U.S., 23 states allow legal marijuana use in some form, and four of those states (Alaska, Oregon, Washington and Colorado) have legalized recreational use and many other states are considering it. If you’re thinking about getting a prescription for medical marijuana or live in a state where recreational use is legal, here are some questions you should ask first:
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- How does marijuana work in my body?
- What are the common short-term effects?
- What's known about long-term safety and adverse effects?
- Are there ways to use it safely and is one way of taking the drug better than another?
Marijuana is the most common name for plants belonging to the genus Cannabis. The leaves, flowers and buds can all contain the active chemicals that give marijuana its psychoactive effects. The various species of marijuana plants contain many active chemicals called cannabinoids that are present in different proportions and potencies depending on the particular plant and how it is prepared for use.
THC (tetrahydrocannabinol) is the cannabinoid we understand the best; it’s responsible for most of the psychoactive properties of cannabis. Marijuana has gotten stronger since Cheech and Chong’s days; the concentration of THC in marijuana plants has risen from 1-3 percent in the 1970s to more than 8 percent (and in some varieties, much higher than this) today.
What are Synthetic Cannabinoids?
These increasingly popular analogs of natural chemicals found in marijuana are added to (often sprayed on) other herbs or spices. These synthetics have various street names -- K2 and Spice are probably the most popular. They can be quite potent and aren’t carefully regulated, so it’s no surprise emergency rooms are reporting a huge increase in visits due to the use of synthetic cannabinoids. Patients can appear either lethargic and dull -- similar to an opioid overdose -- or highly agitated and aggressive. There is no antidote other than time.
How Does Medical Marijuana Differ?
Medical marijuana is simply marijuana used for medical purposes. Certain synthetic cannabinoid preparations, e.g. dronabinol and nabilone, are also available as oral pills and their effects are slower than smoked marijuana. Although the data supporting the efficacy of medical marijuana are still far from what we would like to see, it's been used (and is still being studied) in people with chronic pain, multiple sclerosis, brain injuries and dementia, nausea and vomiting (especially from chemotherapy), epilepsy, glaucoma and many other symptoms and disorders.
How Does Marijuana Work in the Body?
When inhaled, cannabinoids are rapidly absorbed by the lungs and are distributed throughout the body within minutes. In the brain, they bind to specific receptors on nerve cells and cause the drug’s many psychoactive effects. Receptors are present on other cells in the body as well, including cells of the immune system, and these may account for some of the other effects of the drug.
When the drug is inhaled, psychoactive effects begin with a couple of minutes, peak at about 30 minutes, and last on average about three hours. When cooked into food or added to a beverage, the onset of the drug’s effects takes much longer and the duration of the effects is longer as well. The body stores THC in fat deposits for several weeks and is only slowly eliminated; urine tests may be positive up to one month.
What are the Short-Term Effects?
On the positive side of the ledger, most people typically feel happy, relaxed and comfortable. They also feel hungry. For many patients with chronic pain, the pain lessens. However, there is a negative side to things as well. Most people don’t experience these side effects, but they can include:
- anxiety and paranoia
- impaired judgment and coordination
- nausea and vomiting
- diminished short-term memory
- red eyes
- dry mouth
- rapid heartbeat
What are the Long-Term Effects?
Surprisingly, we know very little about long-term effects. Because marijuana has been an illegal substance for so long, research has been limited and only now are we figuring out what the long-term effects are. By and large, it appears to be much safer than alcohol or tobacco use, but there is still reason for concern:
- Marijuana is addicting, although not nearly as addicting as nicotine, alcohol, cocaine or heroin. However, many long-term users experience all the signs of addiction: dependence, tolerance, an inability to stop and withdrawal symptoms.
- In adolescents, it may impair proper brain development. Studies of brain scans confirm that this effect is real and changes in brain function can be demonstrated even in casual users. There's evidence that marijuana use by people 18 and younger can lead to cognitive and neuropsychiatric issues that can persist into adulthood. It also may lower IQ scores, although these data are controversial.
- It has been linked to a variety of mental-health disorders, such as psychosis, but we don’t know if this link is causal or just correlative (i.e. does marijuana use cause the problem or is using marijuana something that people prone to certain mental disorders do?)
- The impact on your lungs and heart is not understood, but is almost certainly less than that of tobacco use. Similarly, if there’s an increased cancer risk, it is small and again much less than that associated with tobacco use.
- Some adolescents who use marijuana experience what some experts call amotivational syndrome, which is just what it sounds like: A slacker state of lethargy that can affect school performance and social behavior.
- Long-term use can suppress testosterone levels in men, leading to a lowered libido, and there is evidence that sperm counts and the quality of sperm can be adversely affected.
For people who live in states where recreational marijuana is legal, it can be enjoyed responsibly if you follow a few simple guidelines:
- Don’t mix it with other drugs or alcohol. Ever.
- Don’t use it if you’re 18 years of age or younger.
- Don’t use it if you’re expecting or think you may be pregnant.
- If you’re on prescription medications, check with your healthcare provider to make sure there are no interactions you need to be concerned about.
- Use it in a proper setting, while you’re relaxed and with people you trust, and never before work, school or while driving. A couple of puffs at the end of a day can be relaxing, but know how it affects you. It simply isn’t for everyone.
- If you can use marijuana without issue, a couple of puffs should be enough. There’s also no need to hold your breath after you take a puff -- almost all of the active chemicals are absorbed into your body almost instantly.
- Some people worry about other chemicals, many of which are also in tobacco smoke, that may be present in inhaled marijuana. It’s true that chemicals such as formaldehyde, ammonia and cyanide occur in marijuana smoke. Hookahs and water pipes don’t remove these chemicals. However, vaporizers do -- they don’t burn the marijuana at the same high temperatures found in joints and hookahs, and although we don’t yet know for sure, vaping may be the safest delivery system.
- If you choose to eat marijuana (the infamous brownies), wait at least two to three hours to feel the full effect. Don’t keep eating more out of impatience -- you may soon find yourself effectively overdosed and quite possibly in trouble.
Malcolm Thaler, M.D. is a physician at One Medical Group. He is the author and chief editor of several best-selling medical textbooks and online resources, and has extensive expertise in managing a wide range of issues, including the prevention and treatment of cardiovascular disease, diabetes and sports injuries.
Dr. Thaler graduated magna cum laude from Amherst College, received his M.D. from Duke University and completed his residency in Internal Medicine at Harvard's New England Deaconess Hospital and Temple University Hospital. He is certified through the American Board of Internal Medicine.