The use of cannabis, like any other substance, carries with it the risk of side effects. Some can be laughed off (among friends, of course), while others are more serious. One’s particular risk of side effects can only be assessed by looking at the totality of one’s circumstances. The presence of a pre-existing medical condition, the use of substances other than marijuana, and the biological differences between individuals all dictate whether or not someone will experience any of these side effects. The potential side effects outlined below should be interpreted in that context; remember, only a duly licensed medical practitioner can diagnose actual side effects from the use of cannabis. Also, nearly all side effects reported in peer-reviewed journals contain the caveat that more studies are warranted since the study of the side effects of cannabis in its various forms is an emerging discipline. Thankfully, as more medical professional prescribe cannabis as a viable medical alternative to traditionally prescribed medication, and as more voters in more states and provinces allow for its use, more studies will follow.

Acute Side Effects

There are numerous acute side effects of cannabis. Most of these are known and even sought after either for medicinal purposes or recreational ones. The majority of marijuana users and non-users alike are aware that the use of cannabis can cause an increase in appetite, a sense of relaxation or well-being, and altered senses of time and perception. Other acute side effects some users of cannabis may experience include dry mouth and dizziness. These side effects are short-lived for most.

What many individuals do not know is that the use of cannabis, even occasionally, can increase the user’s heart rate by up to 50 percent. It can also affect the user’s blood pressure. A user’s blood pressure can increase while standing, and decrease while sitting. The acute side effect to be most wary of is the psychomotor impairment that can cause accidents or even death of users and those around them. The incidences of this, though, pales in comparison to the similar effect provided by alcohol and its abusers.

Chronic Side Effects

The potential chronic effects of cannabis are things that heavy users should consider and weigh against the benefits of using it. Most of the chronic effects of cannabis use are attributed to the smoking of marijuana and not so much for to the ingestion of edible concoctions or pills. When users smoke marijuana over long periods of time, or in high quantities for shorter periods of time, they are at risk for many of the same respiratory issues that smokers of tobacco subject themselves to. The compromise of lung functions can lead to chronic bronchitis, coughing and wheezing, as well as an increase in the occurrence of lung cancers. One study found that smokers who only used cannabis or other non-tobacco products had higher incidences of pulmonary function issues when compared to smokers of tobacco alone. Of course, peer groups within the study who smoked neither were unsurprisingly found to have better lung function than either group.

Another chronic side effect of high amounts of THC, regardless of ingestion method, is lower testosterone levels and sperm counts in male users. However, the most serious side effect of long-term, high-volume cannabis usage in younger adults is premature mortality. A Swedish study of heavy cannabis users (as defined by having smoked marijuana more than 50 times by age 18) had a highly increased chance of premature death, especially violent deaths, than their non-consuming peers.

Cannabis as Medicine

When cannabis is used as a medicine, its side effects are often the rationale behind it being prescribed. Sufferers of such diverse afflictions as cancer, AIDS, fibromyalgia, and other neuropathic pain are routinely prescribed cannabis for many of its beneficial acute side effects such as pain mitigation, nausea abatement, and appetite stimulation. Some patients of these afflictions, however, may experience negative side effects such as changes in mood (for the worse), increased anxiety, and even paranoia. It is worth noting that these negative side effects are almost always associated with individuals that have smoked cannabis versus those that have ingested it in some other form.

A notable exception is that some studies on sufferers of multiple sclerosis have not shown that medications containing cannabis as significantly more beneficial or more detrimental than their non-cannabinol counterparts.

CBD vs. THC

Nearly all the negative side effects mentioned above are attributed to the use of cannabis containing high levels of delta-9-tetrahydrocannabinol (THC). The presence of cannabidiol (CBD) seems to mitigate adverse effects of THC in medications, though. When combined with CBD in a recently developed nasal spray, THC has been shown to pose no harmful side effects. A plethora of studies have shown patients being prescribed CBD are well tolerated and safe for both in vivo and in vitro humans.

It should be noted that CBD concentrations are variable and in some instances where concentrations are high, some side effects have been reported. However, even when side effects are proven in double-blind studies to be due to the use of CBD, patients overwhelmingly prefer the medications containing CBD than other traditionally-prescribed alternatives.