MARIJUANA - INNOCENT? HARMLESS? HARDLY!
When smoked, it begins to effect users almost immediately and can last for one to three hours. When it is eaten in food, such as baked in brownies and cookies, the effects take longer to begin, but usually last longer.
The short-term effects of marijuana include:
Distorted perception (sights, sounds, time, touch)
Problems with memory and learning
Loss of coordination
Trouble with thinking and problem-solving
Increased heart rate, reduced blood pressure
Sometimes marijuana use can also produce anxiety, fear, distrust, or panic.
Effects on the Brain
The active ingredient in marijuana, delta-9 tetrahydrocannabinol or THC, acts on cannabinoid receptors on nerve cells and influences the activity of those cells. Some brain areas have many cannabinoid receptors, but other areas of the brain have few or none at all. Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement.
When high doses of marijuana are used, usually when eaten in food rather than smoked, users can experience the following symptoms:
Effects on the Heart
Within a few minutes after smoking marijuana, the heart begins beating more rapidly and the blood pressure drops. Marijuana can cause the heart beat to increase by 20 to 50 beats per minute, and can increase even more if other drugs are used at the same time.
Because of the lower blood pressure and higher heart rate, researchers found that users' risk for a heart attack is four times higher within the first hour after smoking marijuana, compared to their general risk of heart attack when not smoking.
Effects on the Lungs
Smoking marijuana, even infrequently, can cause burning and stinging of the mouth and throat, and cause heavy coughing. Scientists have found that regular marijuana smokers can experience the same respiratory problems as tobacco smokers do, including:
Daily cough and phlegm production
More frequent acute chest illnesses
Increased risk of lung infections
Most marijuana smokers consume a lot less cannabis than cigarette smokers consume tobacco, however the harmful effects of smoking marijuana should not be ignored. Marijuana contains more carcinogenic hydrocarbons than tobacco smoke and because marijuana smokers typically inhale deeper and hold the smoke in their lungs longer than tobacco smokers, their lungs are exposed to those carcinogenic properties longer, when smoking.
Research indicates that THC impairs the body's immune system from fighting disease, which can cause a wide variety of health problems. One study found that marijuana actually inhibited the disease-preventing actions of key immune cells. Another study found that THC increased the risk of developing bacterial infections and tumors.
How Does Marijuana Affect the Brain?
Scientists have learned a great deal about how THC acts in the brain to produce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to the brain and other organs throughout the body.
THC acts upon specific sites in the brain, called cannabinoid receptors, kicking off a series of cellular reactions that ultimately lead to the "high" that users experience when they smoke marijuana. Some brain areas have many cannabinoid receptors; others have few or none. The highest density of cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thinking, concentrating, sensory and time perception, and coordinated movement.1
Not surprisingly, marijuana intoxication can cause distorted perceptions, impaired coordination, difficulty with thinking and problemsolving, and problems with learning and memory. Research has shown that, in chronic users, marijuana's adverse impact on learning and memory can last for days or weeks after the acute effects of the drug wear off.2 As a result, someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all of the time.
Research into the effects of long-term cannabis use on the structure of the brain has yielded inconsistent results. It may be that the effects are too subtle for reliable detection by current techniques. A similar challenge arises in studies of the effects of chronic marijuana use on brain function. Brain imaging studies in chronic users tend to show some consistent alterations, but their connection to impaired cognitive functioning is far from clear. This uncertainty may stem from confounding factors such as other drug use, residual drug effects, or withdrawal symptoms in long-term chronic users.
Long-term marijuana abuse can lead to addiction; that is, compulsive drug seeking and abuse despite the known harmful effects upon functioning in the context of family, school, work, and recreational activities. Estimates from research suggest that about 9 percent of users become addicted to marijuana; this number increases among those who start young (to about 17 percent) and among daily users (25-50 percent).
Long-term marijuana abusers trying to quit report withdrawal symptoms including: irritability, sleeplessness, decreased appetite, anxiety, and drug craving, all of which can make it difficult to remain abstinent. These symptoms begin within about 1 day following abstinence, peak at 2-3 days, and subside within 1 or 2 weeks following drug cessation.3
Marijuana and Mental Health
A number of studies have shown an association between chronic marijuana use and increased rates of anxiety, depression, and schizophrenia. Some of these studies have shown age at first use to be an important risk factor, where early use is a marker of increased vulnerability to later problems. However, at this time, it is not clear whether marijuana use causes mental problems, exacerbates them, or reflects an attempt to self-medicate symptoms already in existence.
Chronic marijuana use, especially in a very young person, may also be a marker of risk for mental illnesses - including addiction - stemming from genetic or environmental vulnerabilities, such as early exposure to stress or violence. Currently, the strongest evidence links marijuana use and schizophrenia and/or related disorders.4 High doses of marijuana can produce an acute psychotic reaction; in addition, use of the drug may trigger the onset or relapse of schizophrenia in vulnerable individuals.
What Other Adverse Effect Does Marijuana Have on Health?
Effects on the Heart
Marijuana increases heart rate by 20-100 percent shortly after smoking; this effect can last up to 3 hours. In one study, it was estimated that marijuana users have a 4.8-fold increase in the risk of heart attack in the first hour after smoking the drug.5 This may be due to increased heart rate as well as the effects of marijuana on heart rhythms, causing palpitations and arrhythmias. This risk may be greater in aging populations or in those with cardiac vulnerabilities.
Effects on the Lungs
Numerous studies have shown marijuana smoke to contain carcinogens and to be an irritant to the lungs. In fact, marijuana smoke contains 50-70 percent more carcinogenic hydrocarbons than tobacco smoke. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which further increase the lungs' exposure to carcinogenic smoke. Marijuana smokers show dysregulated growth of epithelial cells in their lung tissue, which could lead to cancer;6 however, a recent case-controlled study found no positive associations between marijuana use and lung, upper respiratory, or upper digestive tract cancers.7 Thus, the link between marijuana smoking and these cancers remains unsubstantiated at this time.
Nonetheless, marijuana smokers can have many of the same respiratory problems as tobacco smokers, such as daily cough and phlegm production, more frequent acute chest illness, and a heightened risk of lung infections. A study of 450 individuals found that people who smoke marijuana frequently but do not smoke tobacco have more health problems and miss more days of work than nonsmokers.8 Many of the extra sick days among the marijuana smokers in the study were for respiratory illnesses.
Effects on Daily Life
Research clearly demonstrates that marijuana has the potential to cause problems in daily life or make a person's existing problems worse. In one study, heavy marijuana abusers reported that the drug impaired several important measures of life achievement, including physical and mental health, cognitive abilities, social life, and career status.9 Several studies associate workers' marijuana smoking with increased absences, tardiness, accidents, workers' compensation claims, and job turnover.
What Treatment Options Exist?
Behavioral interventions, including cognitive-behavioral therapy and motivational incentives (i.e., providing vouchers for goods or services to patients who remain abstinent) have shown efficacy in treating marijuana dependence. Although no medications are currently available, recent discoveries about the workings of the cannabinoid system offer promise for the development of medications to ease withdrawal, block the intoxicating effects of marijuana, and prevent relapse.
The latest treatment data indicate that in 2008 marijuana accounted for 17 percent of admissions (322,000) to treatment facilities in the United States, second only to opiates among illicit substances. Marijuana admissions were primarily male (74 percent), White (49 percent), and young (30 percent were in the 12-17 age range). Those in treatment for primary marijuana abuse had begun use at an early age: 56 percent by age 14.**
Is Marijuana Medicine?
The potential medicinal properties of marijuana have been the subject of substantive research and heated debate. Scientists have confirmed that the cannabis plant contains active ingredients with therapeutic potential for relieving pain, controlling nausea, stimulating appetite, and decreasing ocular pressure. Cannabinoid-based medications include synthetic compounds, such as dronabinol (Marinol®) and nabilone (Cesamet®), which are FDA approved, and a new, chemically pure mixture of plant-derived THC and cannabidiol called Sativex®, formulated as a mouth spray and approved in Canada and parts of Europe for the relief of cancer-associated pain and spasticity and neuropathic pain in multiple sclerosis.
Scientists continue to investigate the medicinal properties of THC and other cannabinoids to better evaluate and harness their ability to help patients suffering from a broad range of conditions, while avoiding the adverse effects of smoked marijuana.
How Widespread is Marijuana Abuse?
National Survey on Drug Use and Health (NSDUH)***
According to the National Survey on Drug Use and Health, in 2009, 16.7 million Americans aged 12 or older used marijuana at least once in the month prior to being surveyed, an increase over the rates reported in all years between 2002 and 2008. There was also a significant increase among youth aged 12-17, with current use up from 6.7 percent in 2008 to 7.3 percent in 2009, although this rate is lower than what was reported in 2002 (8.2 percent). Past-month use also increased among those 18-25, from 16.5 percent in 2008 to 18.1 percent in 2009.
Monitoring the Future Survey****
Results from the 2009 Monitoring the Future survey show, as in the past few years, a stall in the decline of marijuana use that began in the late 1990s among our Nation's youth. In 2009, 11.8 percent of 8th-graders, 26.7 percent of 10th-graders, and 32.8 percent of 12th-graders reported past-year use. In addition, perceived risk of marijuana use declined among 8th- and 10th-graders, and disapproval of marijuana use declined among 10th-graders. This is a concern because changes in attitudes and beliefs often drive changes in drug use.
Marijuana Use by Students - 2009 Monitoring the Future Survey
8th Grade 10th Grade 12th Grade
Lifetime 15.7% 32.3% 42.0%
Past Year 11.8 26.7 32.8
Past Month 6.5 15.9 20.6
Daily 1.0 2.8 5.2
Occasional marijuana use is rarely seriously harmful, but smoking pot has important medical effects.
Physiological Effects of Marijuana
The active ingredient in marijuana is THC. That's short for delta-9-tetrahydrocannabinol.
THC is rapidly absorbed after smoking pot. Within minutes, THC and the other substances in marijuana smoke cause short-term medical effects.
Signs of using marijuana include:
rapid heart rate
increased blood pressure
increased rate of breathing
increased appetite, or "the munchies"
slowed reaction time
These effects are reduced after three or four hours. However, marijuana hangs around in your system for as long as 24 hours after smoking. The lingering effects mean you're impaired for several hours after the high wears off.
Psychological Effects of Marijuana
The main psychological effect of smoking pot is euphoria. Getting high or "stoned" is the reason most pot smokers use marijuana.
Other short-term psychological effects of pot include:
distorted sense of time
magical or "random" thinking
short-term memory loss
anxiety and depression
These psychological signs of using pot also generally ease after a few hours. But residual effects can last through the next day.
Risks of Marijuana Use
The risks of smoking marijuana go up with heavy use. Although the link has never been proven, many experts believe heavy pot smokers are at increased risk for lung cancer.
Heavy marijuana use lowers men's testosterone levels and sperm count and quality. Pot could decrease libido and fertility in some heavy-smoking men.
Contrary to what many pot smokers may tell you, marijuana is addictive, at least psychologically. Even among occasional users, one in 12 can feel withdrawal symptoms if they can't get high when they want to. Among heavy pot smokers, the rates of dependence are higher.
Many experts also believe that marijuana is physically addictive. Symptoms of withdrawal from pot might include:
Is pot a "gateway" drug? In other words, does smoking marijuana make someone more likely to try cocaine, heroin, ecstasy, and other "hard" drugs? The jury is still out on this one. It's true that pot smokers are more likely to use other drugs after trying marijuana. What's not clear is whether smoking pot causes further drug use or if people who start smoking pot are just more likely to try drugs in general.
If you're wondering how long marijuana stays in your system after smoking, it depends on how often you smoke. Light users -- those who smoke pot once in a while -- will have a negative drug screen after a marijuana-free week. Heavy users -- sometimes called "stoners" -- may continue testing positive for a month after last smoking pot.