Cannabis: Benefits, Side Effects and Dosage

Cannabis has become a topic of intense discussion and interest, both for its potential medical benefits and its possible risks. With legalization expanding globally, more people are curious about what cannabis can actually do, what side effects to watch for, and how to use it responsibly. This detailed guide explores the evidence-based benefits, side effects, and dosage considerations of cannabis, offering an up-to-date, research-driven overview.

Benefits of Cannabis

Cannabis has been used for centuries for its therapeutic properties, but only in recent decades has modern science begun to unravel its complex effects on the human body. From pain relief to potential benefits in certain mental health conditions, cannabis is being explored as an alternative or adjunct to traditional therapies. Yet, while hopeful findings are emerging, the evidence can be inconsistent, and much remains to be clarified by future research.

Condition	Benefit	Evidence Strength	Source(s)
Pain	Reduction	Moderate	3 11 12
Spasticity	Relief (MS)	Moderate	3
Nausea/Vomiting	Reduction (esp. chemotherapy)	Moderate	2 3
Anxiety	Short-term relief	Emerging	2 4
Sleep	Improvement	Weak/Emerging	2 4
PTSD	Potential benefit	Weak/Emerging	2
Epilepsy	Reduction (CBD)	Moderate	2
Obesity/BMI	Lower BMI in users	Theoretical	5

Table 1: Therapeutic Benefits of Cannabis

Pain Management

Chronic and neuropathic pain relief is one of the most commonly cited—and best supported—medical uses for cannabis. Low-dose vaporized cannabis has been shown to significantly reduce pain intensity in patients with treatment-resistant neuropathic pain. Notably, even low doses (1.29% THC) can be as effective as medium doses, suggesting that high doses aren't always necessary for pain relief. The number needed to treat (NNT) for meaningful pain reduction is similar to that of conventional medications, and psychoactive side effects tend to be mild and short-lived at lower doses 3 11. Additionally, patients using cannabis for chronic pain over a year showed no increase in serious adverse events compared to controls, though non-serious side effects were more common 12.

Muscle Spasticity and Movement Disorders

Multiple sclerosis (MS) patients and others with movement disorders may experience relief from muscle spasticity with cannabis-based medicines. Reviews indicate moderate evidence for this benefit, particularly in managing persistent symptoms where other treatments have failed 3.

Nausea and Vomiting

Cannabis, especially synthetic cannabinoids, has been widely used to reduce chemotherapy-induced nausea and vomiting. This benefit is well established, but often reserved for cases where standard antiemetics are insufficient 2 3.

Psychiatric and Neurological Conditions

Research is still emerging for the use of cannabis in psychiatric disorders. Early evidence suggests that cannabidiol (CBD) may help reduce social anxiety, and there are mixed but mainly positive findings for adjunctive use in schizophrenia. There is weak but promising data for improving symptoms of post-traumatic stress disorder (PTSD) and sleep disturbances, though the evidence is currently not robust enough to make broad recommendations 2 4. Notably, CBD has shown potential in reducing seizure frequency in certain forms of intractable childhood epilepsy 2.

Weight and Metabolic Effects

Interestingly, studies suggest that cannabis users tend to have lower body mass index (BMI) and lower rates of obesity, despite increased caloric intake. A theoretical explanation is that cannabis, through its effect on cannabinoid receptors, may increase metabolic rate and reduce energy storage over time 5. However, this area is still primarily speculative and requires further investigation.

Side Effects of Cannabis

While cannabis offers potential benefits, it is not without risks. Understanding the spectrum of side effects—ranging from mild and temporary to more severe and persistent—is essential for informed decision-making. Side effects also vary depending on dose, method of use, frequency, age at first use, and individual vulnerability.

Effect	Severity	Frequency	Source(s)
Anxiety/Panic	Mild to Severe	Common	6 7 8
Psychosis	Moderate-Severe	Less Common	1 6 8 10
Dependence	Moderate	~10% of users	6 7 9 10
Cognitive Impairment	Mild-Moderate	Regular users (esp. adolescents)	1 6 9
Drowsiness/Dizziness	Mild	Common	3 12
Respiratory	Mild-Moderate	Smokers	6 9
Cardiovascular	Mild-Moderate	At-risk groups	6 13
Motor Vehicle Accidents	Moderate	Doubled risk	6 9
Worsening Mental Health	Moderate-Severe	Vulnerable groups	2 10

Table 2: Common Side Effects of Cannabis

Acute Psychological Effects

Anxiety and Panic: Acute anxiety or panic attacks are among the most common psychological side effects, experienced by 22% of users in some surveys. These effects are usually transient but can be distressing 8. High-THC formulations are particularly likely to provoke anxiety, especially in inexperienced users or those with pre-existing mental health conditions 2.

Psychotic Symptoms: A smaller but significant proportion (about 15% in some surveys) report short-term psychotic symptoms, especially after heavy use. People with existing psychiatric disorders, such as schizophrenia, are at higher risk for exacerbation of symptoms or relapse 1 10. The risk is particularly pronounced with high-THC cannabis, and in adolescents or young adults 2 6.

Dependence and Withdrawal

Cannabis can lead to a dependence syndrome in about 1 in 10 regular users. Withdrawal symptoms are generally milder than with substances like alcohol or opioids but can include irritability, sleep disturbances, and cravings 6 7 9 10.

Cognitive and Psychosocial Effects

Regular cannabis use, especially starting in adolescence, is linked to cognitive impairment, including memory and learning issues. There is also an association with early school-leaving and poorer psychosocial outcomes in adulthood. These effects are more pronounced with higher frequency and longer duration of use 1 6 9.

Physical Effects

Respiratory Issues: Smoking cannabis can impair respiratory function, but the extent of risk for respiratory cancer remains unclear, often confounded by concurrent tobacco use 6 9.

Cardiovascular Risks: Cannabis use can increase heart rate and may contribute to cardiovascular disease, especially in middle-aged adults or those with pre-existing conditions 6 13.

Accidents and Safety

Cannabis impairs motor coordination and reaction time, increasing the risk of motor vehicle accidents—risk may be doubled when driving under the influence 6 9.

Other Considerations

• Non-serious Adverse Events: Drowsiness, dizziness, and mild cognitive effects are common, especially when starting or increasing dosage 3 12.
• Worsening of Mental Health: Prolonged or high-THC use can worsen baseline symptoms of depression or anxiety over time, particularly in vulnerable individuals 2 4 10.

Dosage of Cannabis

Navigating the world of cannabis dosing can be confusing due to product variability, individual responses, and lack of standardized guidelines. However, research and clinical experience offer some principles to promote safer and more effective use.

Factor	Recommendation	Rationale	Source(s)
THC Dose	≤30 mg/day (total, oral equivalent)	Limit psychoactive effects	13
CBD Dose	Higher doses often needed	Less potent, reduces THC side effects	13 15
Titration	Start low, go slow	Minimize side effects	13
Standard Unit	5 mg THC per unit	For consistent measurement	14
Method	Vaporization/Oral preferred	Smoking = more respiratory risk	13 14
Driving	Avoid after use	Risk of impairment	6 13

Table 3: Dosing and Administration Guidelines

Principles of Safe Dosing

Start Low, Go Slow: The best practice is to begin with the lowest possible dose and increase gradually, allowing up to two weeks for titration. This approach minimizes the risk of side effects, especially for those new to cannabis or using higher-THC products 13.

THC vs. CBD: THC is the main psychoactive component, responsible for most of the intoxicating and some adverse effects. Daily THC intake should generally not exceed 30 mg (oral equivalent) to avoid significant psychoactive effects and the development of tolerance 13. CBD, in contrast, is less potent, may require higher doses, and can help counteract some negative effects of THC, such as anxiety and rapid heartbeat 13 15.

Standardizing Doses: To address the variability in cannabis products, a "Standard THC Unit" has been proposed at 5 mg of THC, regardless of the method of administration. This helps users and clinicians to better compare products and track intake 14.

Methods of Administration

• Vaporization: Offers rapid onset and allows for more precise dose control. Low-dose vaporized cannabis (1.29% THC) has shown efficacy for pain with minimal cognitive effects 11 13.
• Oral (edibles, oils): Slower onset and longer duration. Doses should be titrated carefully due to delayed effects, which can lead to accidental overconsumption 13.
• Smoking: Delivers cannabinoids quickly but carries more respiratory risks and is not recommended for long-term medical use 13 14.

Special Populations and Safety Considerations

• Avoid high-THC products in youth, people with anxiety, psychosis, or cardiovascular/respiratory conditions, and during pregnancy or breastfeeding 2 13.
• Regular monitoring for side effects, especially during dose changes.
• Never drive or operate heavy machinery after using cannabis, as impairment can persist for several hours 6 13.

Conclusion

Cannabis is a complex plant with both promising benefits and notable risks. While it can offer relief for pain, spasticity, and certain neurological or mental health conditions, side effects—ranging from mild anxiety to dependence and cognitive impairment—are important to consider. Safe and effective use depends on understanding individual needs, dosing principles, and the variability of cannabis products.

Key Takeaways:

• Cannabis shows moderate evidence for pain, spasticity, nausea, and epilepsy relief, with emerging potential in psychiatric and sleep disorders 2 3 11.
• Side effects range from acute anxiety and mild cognitive changes to dependence, psychosis, and increased accident risk—especially at higher doses and in vulnerable individuals 6 8 9 10.
• Dosage should be individualized: start low, titrate slowly, favor lower-THC products, and use standardized dosing units when possible 13 14.
• Avoid high-risk situations such as driving after use and avoid high-THC products in those at risk for mental health or cardiovascular issues 2 6 13.
• Much remains to be learned—ongoing research and personalized, cautious use are crucial for maximizing benefits and minimizing harms.

By staying informed and using cannabis wisely, individuals and clinicians can navigate this evolving landscape with greater safety and confidence.