The Health Effects of Cannabis

The following is a brief summary of the most common physiologic effects of cannabis on each of our bodily systems.

Nervous System:

Cannabinoids have been shown to reduce the intensity of pain, including inflammatory pain, neuropathic pain, and cancer pain. Cannabinoids reduce spasticity and the pain associated with muscle spasm.  Beyond decreasing the intensity of pain, many patients report that cannabis changes the nature of the pain, making it more bearable and less distracting.  In certain situations, cannabinoids can increase the intensity of acute pain.  Cannabinoids have neuroprotective effects, protecting the nerves from acute injuries like head trauma and stroke, and from conditions that cause chronic injury, such as Alzheimer’s disease.  They have anticonvulsant effects, and in some circumstances, antipsychotic effects.

Cannabinoids also affect our consciousness via the nervous system.  Depending on the strain or preparation, cannabinoids can be awakening or sedating.  Cannabinoids can slow reaction time and cause other changes in sensory perception.  Many patients report positive mood, relaxation, laughter, social comfort, time distortion, and the intensification of ordinary experiences (e.g. eating, sex, listening to music) after using cannabis.  Cannabis can cause both a dissociative effect (awareness detaching from the physical body and one’s environment) and, conversely, an integrating effect (greater awareness of self and environment).

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Digestive System

Cannabis has broad effects in the digestive system, including increasing appetite, reducing nausea and vomiting, inhibiting acid secretion, relaxing smooth muscle, decreasing pain, decreasing inflammation, and decreasing motility, thereby relieving cramps and diarrhea.  Cannabinoids are active in the liver and can modulate inflammation and scarring. Cannabis decreases saliva production, resulting in dry mouth, and enhances the perception of flavors.

Metabolism

Cannabinoids influence the hormones that control appetite and fat metabolism.  Despite increasing appetite, several studies have now shown that cannabis users are less likely to be obese and diabetic than their non-cannabis using counterparts.  Underweight patients with chronic disease have also used cannabis to gain weight – as in other bodily systems, cannabinoids have the potential to bidirectionally restore balance, potentially helping both overweight and underweight individuals.

Cardiovascular system

Cannabis exerts bidirectional effects on the cardiovascular system – it can increase or decrease both heart rate and blood pressure.  Typical doses of cannabis slightly decrease blood pressure and increase heart rate.  Cannabinoids can dilate blood vessels, improving blood flow, and animal studies suggest that some cannabinoids could prevent or reduce atherosclerosis (hardening of the arteries).  Ultra-low doses of THC have been shown to limit the damage of heart attack while preserving cardiac function and promoting faster healing.  In general, therapeutic doses of cannabis have a cardioprotective effect, while very high doses of cannabis and synthetic cannabinoids could be dangerous to the heart, especially in patients with pre-existing heart conditions.

Eyes and Ears:

Cannabis can lower the pressure in the eye, and important benefit for those with glaucoma, and the cause of the “red eye” side effect.  Cannabinoids can protect the optic nerve in glaucoma and other diseases of the eye.  Cannabis has also been shown to acutely improve night vision.  While there are reports of cannabis relieving tinnitus (ringing in the ears), there is also some evidence in rats that cannabinoids may promote the development of tinnitus, especially when there is pre-existing hearing damage.  Cannabinoids may also have a role in the development and treatment of inner ear disorders that cause dizziness and vertigo.

Reproductive System

Most human male and female reproductive tissues, such as uterus and testis, manufacture and degrade endocannabinoids to control hormones, fertility, implantation and development of the embryo, and inflammation.  The plant cannabinoids interact with this same cellular machinery, and have the potential to both enhance or inhibit optimal function of these systems.

Cannabis use by pregnant women is difficult to study because controlled experiments are unethical and observational studies are fraught with challenges in reporting and confirming cannabis use, concurrent use of other drugs, and lack of information on dosage.  While few studies have been conclusive, the most consistent evidence of adverse effects associated with  illicit cannabis use during pregnancy are low birth weight, prematurity, and cognitive deficits in the offspring that often resolve as the children age.  Other studies in Jamaican women, who traditionally use cannabis as a tonic during pregnancy and to aid in childbirth, found their offspring to have more resilience to stress, better sleep-wake organization, and improved socialization early in life, but found no differences at age 5.

The safety profile of cannabis in pregnancy, from the little data available, is comparable to other medications in category C (suspected of causing harmful effects on the fetus that may be reversible).  Category C drugs are used in pregnancy only when safer medicines are not available or effective, and the health benefit to mother and baby outweigh the potential harm.  Maternal stress and malnutrition are well known to increase the likelihood of adverse outcomes in pregnancy, and in some situations a healthcare provider may determine that the potential benefits of using cannabis to treat pain, PTSD, seizures, or vomiting in pregnancy outweigh the risks.  Non-smokable delivery methods should always be used to avoid exposing the fetus to carcinogens and other products of combustion.

The cannabinoids, terpenoids, and flavonoids in cannabis all can affect hormone levels, especially when taken acutely.  Long-term cannabis users, however, have normal hormone levels when compared with non-users.  THC has been shown to have a detrimental effect on sperm counts and sperm motility, but regular male users can certainly still produce a pregnancy.  Though a small study reported cannabis causing irregular menstrual cycles in women, many patients report that cannabis can bring balance to their cycle and relieve many premenstrual and menstrual symptoms.  One study found that women with more severe menstrual symptoms had lower levels of their own endocannabinoids, a case for administering additional cannabinoids from a plant source to help with this potential “deficiency.”

Cannabis can affect sexual function, often helping relieve stress, enhance erection, and increase the enjoyment of sexual activity.  It can dry vaginal secretions, like it does in the mouth, so cannabis users may benefit from added lubrication.  From a practical standpoint, cannabis can enhance one’s sex-life if used correctly, but it can also interfere.  Dosage is important – a small dose can be stimulating, while high doses may be too sedating or intoxicating to promote good sex.  Animal and human studies also point to differences amongst genders, with females more consistently stimulated by cannabinoids, and males sometimes stimulated and sometimes inhibited.

Soft Tissue and Joints

Cannabinoids can modulate bone remodeling, oftening promoting bone growth and inhibiting bone resorption, and some are currently being studied for prevention and treatment of osteoporosis.  Our bodies increase the number of cannabinoid receptors present in tissues that are injured or inflamed, indicating a role for cannabinoids in healing.  Several cannabinoids have in fact, been shown to prevent cartilage breakdown in joints, protect connective tissue from injury due to lack of oxygen, and speed the repair process in damaged skeletal muscle.  Extensive research has shown that cannabinoids are excellent for reducing muscle spasm and associated symptoms, even in refractory cases of multiple sclerosis or spinal cord injury.  Patients often report improved flexibility and enhanced recovery following exercise when using cannabis.

Respiratory System

Cannabis can dry upper respiratory secretions, similar to its action on saliva and vaginal secretions, which may be of benefit to individuals with a runny nose or severely-ill patients at risk of choking on secretions.  Cannabis has been shown to dilate, or open, the airways in the lungs, potentially improving oxygen intake.  It can act as an expectorant, helping clear phlegm.  Patients have reported using vaporized cannabis to help with asthma and COPD.

Cannabis smoke is clearly irritating to the respiratory system.  The heat can destroy tiny hairs on the respiratory tissue whose job is to help remove phlegm and trapped particles, and some of the smoke’s components can likely cause irritation and inflammation.  While even long term, heavy cannabis smokers do not have an increased risk of lung cancer, they do tend to have more respiratory symptoms like cough, phlegm, and wheeze.  Smoking both tobacco and marijuana synergistically increase the risk of respiratory symptoms and COPD.  Patients with respiratory symptoms should avoid cannabis smoke and consider using alternative delivery methods.

Immune System

The immune system is partially controlled by our body’s own cannabinoids, and using cannabis can certainly affect immune function in complex ways, often suppressing certain aspects of the immune system while stimulating others.  Over-all, cannabinoids have anti-inflammatory properties, and have shown benefit in inflammatory conditions such as Crohn’s disease and multiple sclerosis.  Cannabinoids, terpenes, and other substances in the plant also have antibacterial properties, including potent activity against antibiotic resistant infections like MRSA.

Cancer

Cannabinoids have been shown to target and affect cancer cells differently than normal, healthy cells.  In various types of cancer, cannabinoids have been shown to prevent tumor growth, trigger cell death, prevent the formation of blood vessels that feed the tumor, and inhibit the metastasis of cancer from one part of the body to another.  While we are still very early in our understanding of how to best use cannabis to fight different types of cancer, it is well-established that cannabis can help with the symptoms of cancer and the side effects of cancer treatment, and can be used to enhance the anticancer effects of conventional treatments.

By Dustin Sulak, DO

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How does marijuana work therapeutically? Dr. Sulak explains…

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