Why Using Cannabis to Stimulate Appetite is Problematic
Cannabis and cannabinoids should not be used for appetite stimulation in patients with chronic illnesses like cancer or HIV/AIDS because the evidence shows they are ineffective for improving appetite or weight gain, while carrying significant risks of neuropsychiatric adverse events, cardiovascular complications, and potential for cannabis use disorder. 1
Lack of Efficacy
The 2017 ESPEN guidelines explicitly state there are insufficient consistent clinical data to recommend cannabinoids to improve taste disorders or anorexia in cancer patients, with a low level of evidence. 1
Key Clinical Trial Failures
In a prospective randomized placebo-controlled multi-center trial of 164 patients with advanced cancer and anorexia-cachexia syndrome, cannabis extract or THC at 5 mg per day for 6 weeks did not improve appetite or quality of life. 1
In a head-to-head comparison of 469 patients with cancer cachexia, dronabinol (2.5 mg twice daily) was inferior to megestrol acetate (800 mg/day) for appetite and weight gain, with the progestin group showing significantly greater improvements. 1
A 2022 systematic review found that efficacy was demonstrated in only one of five included trials, and even that single positive study showed improvements only in secondary outcomes like chemosensory perception, not primary appetite measures. 2
A 2013 Cochrane review on HIV/AIDS patients concluded that despite dronabinol being registered for AIDS-associated anorexia, evidence for efficacy and safety is lacking, with studies being short-duration, small, and focused on short-term measures. 3
Significant Adverse Events
Neuropsychiatric Risks
The main adverse events associated with cannabinoid use are euphoria, hallucinations, vertigo, psychosis, and cardiovascular disorders. 1
In elderly patients, cannabinoid administration may induce delirium, making it particularly dangerous in vulnerable populations. 4
Ten percent of adults with chronic cannabis use develop cannabis use disorder, characterized by using more cannabis than expected and difficulty cutting back, with clinically significant impairment. 1
Cannabis use is associated with increased risk for developing depressive disorders and may exacerbate psychiatric disorders in vulnerable individuals. 1
Early onset of cannabis use, especially weekly or daily use, strongly predicts future dependence. 1
High Dropout Rates Due to Adverse Effects
In a small phase II clinical trial testing dronabinol at 5 mg/day, there was a high drop-out rate due to adverse events, despite 68% of patients reporting reduced anorexia. 1 This indicates that even when some subjective benefit is perceived, the tolerability is poor enough that patients cannot continue treatment.
Cardiovascular and Other Physical Risks
Cardiovascular side effects may include arrhythmias and orthostatic hypotension. 1
Cannabinoid hyperemesis syndrome can develop after long-standing cannabis use (>4 times per week for over a year), characterized by cyclical emetic episodes that paradoxically worsen the very symptoms cannabis is meant to treat. 1
Cannabis users are more than twice as likely to be involved in motor vehicle crashes, with fatal accidents involving cannabis increasing from 9.0% in 2000 to 21.5% in 2018. 1
Withdrawal Symptoms
Long-term daily cannabis users may experience withdrawal symptoms after cessation, including irritability, restlessness, anxiety, sleep disturbances, appetite changes, and abdominal pain, lasting up to 14 days. 1
Superior Alternatives Exist
Megestrol Acetate: The Evidence-Based First Choice
Megestrol acetate (400-800 mg/day) is recommended as the primary pharmacological intervention for appetite stimulation in patients with serious illness when increased appetite is important for quality of life. 4, 5, 6
Approximately 1 in 4 patients treated with megestrol acetate will experience increased appetite and 1 in 12 will have measurable weight gain, which, while modest, represents a clear benefit over cannabinoids. 4, 5
The 2017 ESPEN guidelines give progestins a HIGH level of evidence for increasing appetite in anorectic cancer patients with advanced disease, in stark contrast to the LOW level of evidence for cannabinoids. 1
Other Effective Options
Dexamethasone (2-8 mg/day) may be considered for short-term appetite stimulation in patients with limited life expectancy due to its rapid onset of action. 4, 5
Mirtazapine can be useful for appetite stimulation, particularly in patients with concurrent sleep difficulties or mood disorders. 4
Olanzapine (5 mg/day) may be considered, especially for patients with concurrent nausea or anxiety. 4
The Regulatory and Practical Context
Cannabis prescription must follow strict rules because it is listed as a narcotic and psychotropic drug, adding administrative burden without clinical benefit. 1
A randomized trial found that participants who received a medical cannabis card had almost two times greater incidence (17% versus 9%) of developing cannabis use disorder within 12 weeks than controls without a medical cannabis card, suggesting that medical authorization may inadvertently facilitate problematic use. 1
Clinical Bottom Line
The evidence is clear: cannabinoids fail to deliver meaningful improvements in appetite, oral intake, weight, or quality of life in cancer or HIV/AIDS patients, while exposing them to neuropsychiatric risks, cardiovascular complications, and potential for substance use disorder. 1, 2, 7
Address reversible causes of anorexia first (pain, constipation, nausea/vomiting, depression, oropharyngeal candidiasis), then provide nutritional counseling with oral supplements, and only then consider pharmacological appetite stimulants—but choose megestrol acetate or corticosteroids, not cannabinoids. 4, 5
The 2024 ASCO guidelines on cannabis in cancer care do not support its use for appetite stimulation, focusing instead on other indications where evidence is stronger (such as chemotherapy-induced nausea). 1 The consistent message across all major guidelines is that cannabinoids should not be recommended for appetite stimulation in chronic illness.