Safety Research

An important aspect of any medical treatment is making sure it’s safe and effective.

Author and pharmacologist Dr. Nichol Iverson explained the dosing testing that has been conducted to date:

“Laboratory animals (rats, mice, dogs and monkeys) can tolerate doses of up to 1000 mg/kg. This would be equivalent to a 70 kg person swallowing 70g of the drug—about 5,000 times more than is required to produce a high. Despite widespread illicit use of cannabis, there are very few, if any, instances of people dying from an overdose.”

In 1988, the Drug Enforcement Administration’s Law Judge, Francis Young—responding to a petition to reschedule cannabis under the Controlled Substances Act (to make it easier to conduct research into its efficacy)—said, “In strict medical terms, marijuana is far safer than many foods we commonly consume…. Marijuana, in its natural form, is one of the safest therapeutically active substances known to man. By any measure of rational analysis, marijuana can be safely used within the supervised routine of medical care.”

The Institute of Medicine (IOM), more than 10 years later, when investigating the physiological risks of cannabis use, concludedthat “Marijuana is not a completely benign substance. It is a powerful drug with a variety of effects. However, except for the harms associated with smoking, the adverse effects of marijuana use are within the range of effects tolerated for other medications.”

Research conducted on the long-term effects of cannabis use since the IOM report has revealed that consumption of moderate amounts of cannabis to be remarkably safe, particularly when compared to other therapeutically active substances — most significantly is the relative lack of overdose risk. According to a 1995 review prepared for the World Health Organization, “there are no recorded cases of overdose fatalities attributed to cannabis”. Furthermore, a review of clinical investigations and observational studies detailed that investigators “did not find a higher incidence rate of serious adverse events associated with medical cannabinoid use.”

Toxicity and Overdose Risk

It is estimated that to overdose, an average sized human would need to consume 1,500 pounds of cannabis in 15 minutes—an act that is truly not possible. Using a system called LD50, which indicates the lethal dose of a drug or substance for 50 percent of the population, researchers have determined that cannabis is one of the safest substances known and one from which it is theoretically impossible to overdose. Dr. Lester Grinspoon, a psychiatry professor at Harvard Medical School, wrote the following in 1995 in the Journal of the American Medical Association:

“One of marihuana’s greatest advantages as a medicine is its remarkable safety. It has little effect on major physiological functions. There is no known case of a lethal overdose; on the basis of animal models, the ratio of lethal to effective dose is estimated as 40,000 to 1. By comparison, the ratio is between 3 and 50 to 1 for secobarbital and between 4 and 10 to 1 for ethanol [alcohol].

“Marihuana is also far less addictive and far less subject to abuse than many drugs now used as muscle relaxants, hypnotics, and analgesics. The chief legitimate concern is the effect of smoking on the lungs. Cannabis smoke carries even more tars and other particulate matter than tobacco smoke. But the amount smoked is much less, especially in medical use, and once marihuana is an openly recognized medicine, solutions may be found; ultimately, a technology for the inhalation of cannabinoid vapors could be developed.”

The technology to which Dr. Grinspoon alluded is now available via desktop and pocket vaporizers from dozens of manufacturers. Because research regarding the rate of lung cancer and pulmonary diseases, even among chronic cannabis consumers, has shown that marijuana smokers experience no greater risk of lung cancer or related diseases. In fact, research has demonstrated that heavy cannabis smokers are at no greater risk of lung cancer than non-smokers.

Despite these findings, cannabis can’t be considered “harmless.” It delivers a variety of physiological effects, including dilation of blood vessels and rapid heart rate. In very limited cases, especially among those with cardiac conditions, these symptoms can be dangerous. However, these adverse effects are well within the range of other FDA-approved medications. Also, because of tolerance building, users often overcome such reactions to the herb.

Dr. Grinspoon added: “The greatest danger in medical use of marihuana is its illegality, which imposes much anxiety and expense on suffering people, forces them to bargain with illicit drug dealers, and exposes them to the threat of criminal prosecution.”



The short-term effects of cannabis begin only minutes after the flowers of the plant (called “bud”) are smoked or vaporized (“vaped”). If eaten, the effects are perceived about an hour after ingestion. The effect of smoked or vaped cannabis remains for one to four hours (depending on the potency of the particular cannabis), while those who consume edibles experience efficacy for longer periods of time.

Effects may include coughing, euphoria, dry mouth, red eyes, increased appetite (the “munchies”), blurred vision, delayed motor reactions, sedation, and even anxiety. As mentioned, psychoactive effects decrease with continued use (tolerance building). However, in the vast majority of cases, side effects are minimal and can be controlled with dose management (titration).

Although rare, some patients who consume too much cannabis, especially in edible form, sometimes experience temporary anxiety attacks, convulsions, and other negative psychological reactions.


Due to its psychoactive properties, there are concerns with the effects of long-term use of cannabis. Although raw flower cannabis is a strictly prohibited substance at the federal level, with little research and no human trials, the FDA has approved synthetic versions of THC, the primary cannabinoid that delivers both euphoria and medical efficacy. Unlike raw cannabis, which is classified as Schedule I (the most strict drug classification), these derivations of the plant are categorized as Schedule III substances because they are deemed less likely to produce addiction in users.

In 1999, the Institute of Medicine determined that concerns over long-term use of cannabis should be categorized as 1) the effects of consuming whole-plant cannabis and 2) the results of consumption of THC only.

Side Effects of Cannabis

Cannabis has been determined to be one of the safest substances consumed by humans. Thousands of years of anecdotal reports and mounting research evidence has shown that it is impossible to overdose on the substance. Those unfamiliar with its use, however, should understand possible side effects before using the plant (or one of its extracts or concentrates) to treat medical conditions or obtain a euphoric “high.”

  • Uneasiness: Although cannabis consumers typically gain a feeling of comfort and ease—with millions using it to treat anxiety—some experience heightened feelings of anxiety, especially with sativa strains. Strategies for dealing with this include consumption in a safe, familiar environment and eating food. Those who suffer such reactions should purposefully reduce the amount consumed during subsequent sessions. Social stigma and illegality also contribute to the stress experienced by some who consume cannabis.
  • Hunger and Thirst: Cannabis is infamous for stimulating appetite and giving users “the munchies.” Users are encouraged to eat and drink healthy foods instead of sugary junk food. Indica strains are responsible for an increase in appetite, whereas sativa varieties can actually reduce appetite and possibly be an effective treatment for conditions involving obesity or overeating.
  • Red Eye: Cannabis users often experienced a redness of the eyes that is a standard symptom of consumption of the herb. Those concerned that they might be detected should employ eye drops or wear sunglasses.
  • Drowsiness: Just as indica strains of cannabis increase appetite, they often also produce drowsiness (often labeled “couchlock”). Sativa strains produce the opposite effect and result in an energetic, productive high. For this reason, sativa strains are recommended in the morning or midday, while indica types are best for evening and night use.
  • Sleeplessness: Some hybrid and sativa strains of marijuana can produce sleeplessness. If possible, users should understand the type being consumed and the best time of day for use. In a perfect world, patients would possess both indica and sativa strains, giving them the ability to medicate with the variety that is best for their particular situation and time of day.
  • Short-term Memory Loss: Depending on the type and strength of cannabis being consumed, some users may experience short-term memory loss, confusion, or an inability to perform complex tasks requiring focus. For this reason, patients should be familiar with the strength and effects of a particular strain and strive to consume only when appropriate.
  • Euphoria: Nearly all cannabis users report relatively strong feelings of euphoria and being “high” after consumption. Often, situations that normally would elicit no reaction are perceived as humorous or even hilarious. If this type of response might be inappropriate, such as during work hours or when associating with those who might disapprove of the consumption of marijuana, users should avoid consumption until it is safe and acceptable to do so.

Potential Hazards of Smoking Cannabis

Smoke of any type, from any substance, contains several of the same unhealthy chemicals also delivered by tobacco smoke. Some believe that cannabis smoke, like that of tobacco, may increase users’ risk of lung cancer and respiratory diseases. Fortunately for patients consuming cannabis, research has revealed that smoked marijuana produces almost none of the same risks as smoked tobacco.

Studies have revealed that heavy, long-term use may produce bronchitis in users, including a chronic cough (similar to heavy tobacco smokers). Chronic consumers of large quantities of cannabis should consider alternative means of consumption, including edibles and vaporizing.

While some have assumed that smoking cannabis for an extended period of time could increase the risk for lung cancer, in much the same way it does for tobacco, while more research is clearly required, studies to date have not confirmed this negative connection. Consumption of cannabis, smoked or otherwise, has actually been shown to prevent or reduce cancer. Thus, even though cannabis smoke contains some of the same cancer-causing compounds found in tobacco smoke, the efficacy of cannabinoids in marijuana can possibly negate these effects, preventing tumors from forming.

A five-year investigative study was released in 2006 which revealed that even heavy smoking of cannabis does not lead to lung cancer or other types of the disease. The study reported that cannabis may offer compounds (cannabinoids) that control aging cells, preventing them from becoming cancerous.

Other studies have also found that cannabis smokers do not experience an increase in Obstructive Pulmonary Disease, an ailment that is common in heavy tobacco smokers.

Cognitive Effects

Regular or heavy use of cannabis can affect cognition (mental function), especially short-term memory, attention span, and concentration. A 2003 analysis of 15 studies of the effects of cannabis reported:

“There might be decrements in the ability to learn and remember new information in chronic users,” but that “other cognitive abilities are unaffected.”

Psychomotor Effects

When used heavily, cannabis sometimes produces psychomotor impairment characterized by body sway, lack of steadiness in the hands, loss of driving skills and coordination, and a decrease in the ability to focus. These effects tend to be temporary (two to four hours) and do not persist during lack of consumption. These potentially negative effects are actually stronger in those who consume less or are new to the use of cannabis. Prolonged use also seems to enable users to develop compensatory skills as they acclimate to the effects of the herb.

Immune System Effects

Although research on this topic has shown mixed results, cannabis—and the cannabinoids within—have been shown to have a beneficial effect on the body’s immune system. Specialized receptors within the human body (part of something called the endocannabinoid system) have been identified that work in perfect harmony with cannabinoids. All mammals (not just humans) have an endocannabinoid system. This is why cannabis research on animal subjects has yielded relevant research results. Most of these cannabinoid receptors are located in the nervous system (brain, spinal cord, and nerves throughout the body) and immune system, including various organs and tissues.

Some cannabis-centric pharmaceutical companies have developed synthetic cannabinoids and specialized extracts of the whole plant that target these receptors to produce immunosuppressive qualities which may be beneficial to patients suffering from multiple sclerosis, arthritis, HIV/AIDS, and related autoimmune diseases.

In 2012, a study was published that showed cannabinoids actually strengthen the function of the immune system. The study concluded that activation of the specialized receptors of the endocannabinoid system actually has an antiviral effect and showed a reduction in HIV infection rates of 50 percent. Researchers surmised that cannabinoids likely prevent diseased cells from spreading their disease to healthy cells. Other studies involving animals have revealed that cannabinoids reduce viral load, thus helping users more readily heal and fight their disease—or, at a minimum, that they reduce negative symptoms of the disease.