Complementary and Alternative Medicine for Health Professionals
Complementary and alternative medicine (CAM) is the term for medical products and practices that are not part of standard medical care. CAM for cancer care involves the patient’s mind, body, and spirit, and includes multidisciplinary approaches. Evidence-based complementary medicine modalities may be integrated as part of standard cancer care for all patients across the cancer continuum.
Standard treatments are based on scientific evidence from research studies. Despite claims of promising benefits made by CAM treatment providers, many CAM treatments lack good scientific evidence of their safety and effectiveness. Studies are under way to determine the safety and efficacy of many CAM agents and practices for cancer patients.
NCI has evidence-based PDQ information summaries for the integrative, alternative, and complementary therapies listed below.
Summaries Being Regularly Updated
These summaries are reviewed and updated to reflect findings from recent research.
Aromatherapy With Essential Oils (PDQ®)
patient | health professional
Cancer Therapy Interactions With Foods and Dietary Supplements (PDQ®)
patient | health professional
Curcumin (Curcuma, Turmeric) and Cancer (PDQ®)
Prostate Cancer, Nutrition, and Dietary Supplements (PDQ®)
patient | health professional
Summaries No Longer Being Updated
These summaries are no longer being updated. No ongoing studies are being conducted for these topics. The summaries are provided for reference purposes only.
Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.
Cannabis, also known as marijuana, is used to treat some symptoms related to cancer. It’s made from the flowers, leaves, and resin (sticky chemical) of the Cannabis sativa plant.
Cannabis comes in many forms, including vape pens, pills, lozenges, oils, teas, and powder. It isn’t a prescription medication. It can be taken orally (by mouth), by smoking, or by vaporizing.
A licensed doctor or advanced practice provider (APP) must certify you if you want to buy medical marijuana from a registered dispensing facility (a place where medical marijuana is sold).
Cannabis is used to:
- Reduce pain
- Treat glaucoma (eye disease that causes vision loss and blindness)
- Treat nausea (feeling like you’re going to throw up) and vomiting (throwing up) due to cancer treatments
- Treat sleep disorders
- Treat epilepsy (a brain disorder that causes people to have seizures)
- Treat multiple sclerosis (disease that can cause problems with vision, balance, and muscle control)
- Treat mood disorders such as depression, bipolar disorder, and seasonal affective disorder
- Increase appetite
Cannabis also has other uses that haven’t been studied by doctors to see if they work.
Talk with your healthcare providers before taking cannabis. It can interact with some medications and affect how they work. For more information, read the “What else do I need to know?” section below.
Side effects of taking cannabis products may include:
- Drowsiness (feeling sleepy)
- Restlessness (feeling like you can’t relax or get comfortable)
- Anxiety (strong feelings of worry or fear)
- Paranoia (intense thoughts or feelings that someone might try to harm you)
- Hallucinations (seeing or hearing things that aren’t there)
- Feeling hungry
- Short-term memory loss
- Euphoria (feeling very happy or excited)
- Trouble focusing
- Changes in your blood pressure
- Faster heart rate
- Nausea (feeling like you’re going to throw up)
- Vomiting (throwing up)
- Flushing (when your skin becomes red or warm)
- Depression (strong feelings of sadness)
- Insomnia (trouble falling asleep, staying asleep, or waking up too early)
If you’re worried about any of these side effects, talk with your healthcare provider.
Don’t take cannabis products if:
- You have kidney, heart, or liver disease. Cannabis may make these worse.
- You have psychiatric illnesses that affect mood, thinking, and behavior. Cannabis may make these conditions worse.
- You’re taking nivolumab (Opdivo®). Cannabis can lower the response to this medication in patients with advanced melanoma, non-small-cell lung cancer, and renal clear cell carcinoma.
- You’re taking warfarin (Jantoven® or Coumadin®) or other blood thinners. Cannabis can increase your risk of bleeding.
- You’re taking fluoxetine (Prozac®) or disulfiram (Antabuse®). Taking cannabis with these medications can cause confusion, elevated mood, inflated self-esteem, decreased need for sleep, racing thoughts, and trouble focusing.
- You’re on amphetamines (Adzenys XR-ODT, Evekeo ODT). Heart damage may occur with cannabis
- You’re taking atropine (Atropen®). Taking this medication and cannabis can cause heart damage.
- You’re on cocaine. Heart damage may occur with cannabis
- You’re taking pseudoephedrine (such as Sudafed ®), epinephrine (such as Auvi-Q®) or the prescription drug dobutamine (Dobutamine). Taking these medications and cannabis can cause heart damage.
- You’re taking medication that helps you sleep such as lorazepam (Ativan®), diazepam (Valium®), or zolpidem (Ambien®). Taking these medications and cannabis can increase drowsiness.
Don’t give cannabis products to children with epilepsy who are on clobazam (Onfi ® ). Cannabis can increase its side effects
Don’t use medical marijuana for anything other than managing your cancer-related symptoms. Non-medical use of cannabis is illegal under federal law.
For Healthcare Professionals
Cannabis sativa is an annual flowering herb native to East Asia, but is now cultivated around the world. Its uses as a source of industrial fiber, seed oil, and as a recreational agent date back thousands of years across cultures. It has also been employed in traditional medicine as an analgesic, hypnotic, and hallucinogenic, as a sedative, and for reducing inflammation. Preparations containing flowers (marijuana) and leaves; hashish derived from the resinous extract of the plant are consumed orally; by smoking in cigarettes, cigars, pipes, water pipes, or “blunts” (cannabis rolled in the tobacco-leaf wrapper from a cigar); or by vaporizing. Cannabis tinctures, teas, ointments, and oil-based extracts that can be mixed into food products are also popular. It is currently the most widely used illicit agent by more than 147 million people worldwide (1) , and the common route of consumption is via inhalation. Because of the potential for high abuse and dependence, and its classification as a Schedule I agent by the Controlled Substances Act in 1970, cannabis use is a controversial subject in the US.
Pharmacologic investigations over the last few decades revealed cannabinoids (terpenoids) to be the active constituents. Delta-9-tetrahydrocannabinol (THC) is the chief psychoactive component whereas cannabidiol (CBD) is a major secondary non-psychoactive cannabinoid, and may modulate the effects of THC. It has antipsychotic, anticonvulsive, and anxiolytic effects. When co-administered, CBD was reported to mitigate the adverse psychotropic and cardiovascular effects associated with THC (2) .
Small studies have evaluated cannabis for its utility in treating pain, symptoms of neurological disorders, AIDS and cancer.
A systematic review of 18 trials (766 subjects) reported significant relief from pain due to neuropathy, fibromyalgia, rheumatoid arthritis, and mixed chronic pain following cannabinoid use compared to placebo. The interventions included smoked cannabis, oromucosal extracts of cannabis-based medicine, synthetic THC agents dronabinol, nabilone (FDA approved), and a novel THC analogue (3) . But a 4-year prospective study involving 1,514 patients with chronic non-cancer pain did not find evidence that cannabis use decreased pain severity or interference, or exerted an opioid-sparing effect (4) .
In a Cochrane review of four trials involving 48 epileptic patients, short-term CBD use was reported to be well tolerated with no adverse effects, but limited evidence precluded definitive conclusions to be reached on efficacy (5) . Newer randomized studies of patients with either Lennox-Gastaut syndrome or Dravet syndrome, both rare forms of epilepsy, reported effectiveness of Epidiolex, an oral CBD solution, for reducing the frequency of seizures (6) . This is now an FDA-approved drug (7) . Additionally, data indicate benefits of cannabinoids for treating spasticity and neuropathic pain in multiple sclerosis (MS) patients (8) . The American Academy of Neurology issued a Summary of Systematic Reviews for Clinicians indicating that oral cannabis extract is effective in reducing patient-reported spasticity scores and central pain or painful spasms associated with MS (9) .
Conclusions from a large, comprehensive review of 79 trials (6462 subjects) indicate low-quality evidence to address weight gain from HIV infection, sleep disorders, increasing appetite, and for Tourette syndrome, along with elevated risk of short-term adverse effects (10) . The evidence for recommending cannabinoids to treat symptoms of dyskinesia, Parkinson’s and Huntington’s diseases, irritable bowel syndrome, and addiction has been deemed unavailable or insufficient (11) .
In oncologic settings, preclinical findings from 34 studies suggest selective cytotoxic effects of cannabinoids against glioma cells (sparing normal brain cells) via apoptosis, toxicity, autophagy and necrosis (12) . A single clinical trial of 9 patients with recurrent glioblastoma multiforme receiving chemotherapy did not find any benefit with intratumoral THC, but it was well tolerated (13) . Data from another randomized study, involving 21 glioblastoma patients, in which oromucosal whole plant extract nabiximols (contains THC +CBD) was used, have yet to be published (14) .
For symptom management, systematic reviews (10) (15) show that patients who used cannabis-based products experienced less chemo-induced nausea and vomiting compared to those on placebo group or on antiemetics. The differences were not statistically significant and adverse effects including “feeling high,” dizziness, sedation, and dysphoria were reported, resulting in a high dropout rate. Noteworthy are the 2017 American Society of Clinical Oncology (ASCO) guidelines on antiemetics that recommend dronabinol and nabilone for nausea and vomiting, which is resistant to standard therapy (16) .
Findings on effectiveness of cannabis against cancer pain are encouraging. Data from four trials indicate reductions in pain with orally administered THC and with nabiximols spray in advanced cancer patients (17) . An earlier review concluded the evidence level of cannabinoids for alleviating cancer pain as moderate (10) . Cannabis has also been investigated for its role in ameliorating cancer-related anorexia-cachexia syndrome (CACS), but neither cannabis extract nor THC were found effective in improving symptoms or quality of life in a randomized trial of patients with advanced cancer (18) . Additional case reports suggest that dronabinol may be useful for managing persistent symptomatic paraneoplastic night sweats in cancer patients (19) . In one patient with acute lymphoblastic leukemia, a cannabinoid resin extract was reported to affect dose-dependent disease control (20) . In a randomized uncontrolled study, THC-containing medicinal cannabis was found to improve sleep, functional well-being, and quality of life in patients with high grade gliomas (67) . However, a retrospective observational study showed that concomitant use of cannabis during immunotherapy with nivolumab was associated with reduction in tumor response rate in patients with advanced melanoma, non-small-cell lung cancer, and renal clear cell carcinoma. Progression-free survival and overall survival remained unaffected (21) .
Although some data suggest potential benefits, cannabis remains a contentious issue because non-medical use is associated with high risk of addiction, especially when used from an early age (22) (23) ; dependence (24) ; adverse effects (25) ; and with withdrawal syndrome (irritability, sleeping difficulties, dysphoria, craving, and anxiety) (26) that makes cessation tough, eventually leading to relapse. Cannabis use was also reported to elevate the risk of creating false memories (62) .
Recent studies suggest utility of nicotine patch in decreasing negative affect-related withdrawal symptoms in individuals with cannabis use disorder (63) ; and in patients with cannabis dependence, nabiximols combined with psychosocial interventions reduced cannabis use (58) . However, an incentive-based intervention was ineffective in individuals with early psychosis and problematic cannabis use (59) .
It is also important to note that synthetic cannabinoid drugs cause more serious adverse effects compared to natural cannabis, and include respiratory difficulties, hypertension, tachycardia, chest pain, muscle twitches, acute renal failure, anxiety, agitation, psychosis, suicidal ideation and cognitive impairment (27) .
Despite the controversy surrounding cannabis use, California became the first state to legalize it for “medical use” in 1996. As of May 2021, it is available in 35 more states and the District of Columbia (DC) as a medicinal agent, with 16 states and DC also allowing recreational use. Current indications that qualify for medical cannabis use include cancer symptoms, non-cancer pain, glaucoma, AIDS, epilepsy, and MS. However, cannabis use remains illegal under federal law. Following a review of available scientific evidence, the Institute of Medicine (28) , and the National Academies of Sciences, Engineering, and Medicine recommend that further research be done to develop a comprehensive understanding of the health effects of cannabis (11) , which can inform medical cannabis policy. Barriers to research include regulatory issues that involve the FDA, Drug Enforcement Administration, National Institute on Drug Abuse, and Institutional Review Boards; procuring cannabis for studies; and methodological challenges of establishing an acceptable route of administration and standardized doses (29) .