Cannabis for Cancer

How does medical cannabis support cancer treatment?

The role of medical cannabis in oncology has increasingly come into the focus of scientific research in recent years. As the meta-analysis by Castle et al. (2025) shows, there is significant scientific support for the use of medical cannabis both in palliative care and as a potentially cancer-fighting agent. The results from over 10,000 studies, containing a total of 39,767 relevant data points, show that the supportive effect of cannabis in the context of cancer treatment is evidenced 31.38 times more strongly than opposing statements.

Cannabis primarily supports cancer therapy by easing therapy-related side effects such as pain, nausea, and loss of appetite. Furthermore, preclinical studies show a growth-inhibiting effect on tumour cells, with cannabinoids like THC and CBD being able to trigger apoptosis (programmed cell death) and inhibit the proliferation of cancer cells. Learn more about CBD in cancer.

The therapeutic potentials arise mainly through the interaction of cannabinoids with the body's own endocannabinoid system, which plays a regulatory role both in the central nervous system and the immune system. By activating CB1 and CB2 receptors, painful and inflammatory processes can be modulated. The analysis shows that 71.4% of the articles in the overall overview have a predominantly positive sentiment towards medical cannabis.

What health effects does medical cannabis have in cancer treatments?

The health effects of cannabis in cancer treatments can be divided into three main categories: health metrics (e.g., inflammation, therapeutic benefit), cancer therapies (e.g., chemotherapy, immunotherapy, pain management), and cancer dynamics (e.g., tumour growth, apoptosis, remission). The meta-analysis differentiates these categories and assigns each relevant topic a significant correlation with positive or negative sentiments.

The supportive effect is particularly pronounced in the category of health metrics. The correlation between cannabis and therapeutic effects shows a 46.98-fold stronger tendency in favour of supportive statements compared to non-supportive ones. This indicates a very high level of scientific agreement regarding the health-promoting properties of cannabis. Especially noteworthy is the therapeutic effect, which reaches a very high degree of statistical significance with a correlation value of 0.48.

Side effects are also discussed in the literature but are reported less frequently and less strongly than the positive effects. In the sentiment analysis, rejecting statements accounted for only 25.6% of the articles, while unclear results played a minor role with only 3%.

How does cannabis affect inflammation in the body?

Inflammation plays a central role in the development and progression of cancer. Chronic inflammatory processes can not only promote tumour growth but also impair the body's immune response to cancer cells. In this context, the anti-inflammatory effect of medical cannabis is of particular importance. The meta-analysis by Castle et al. (2025) clearly shows that studies dealing with cannabis in connection with inflammatory processes are highly likely to report a supportive effect. The correlation value for anti-inflammatory effects was 0.077 (p < 1.33 × 10⁻¹⁵), indicating very strong statistical significance.

Cannabinoids such as CBD (cannabidiol) and THC (tetrahydrocannabinol) modulate the immune system through various mechanisms. They interact with CB2 receptors, which are mainly found on immune cells, and can inhibit the production of pro-inflammatory cytokines there. These anti-inflammatory properties are not only important for reducing accompanying complaints but could also exert a direct cancer-inhibiting effect by modulating the tumour-promoting inflammatory environment.

A particularly interesting aspect of the meta-analysis is the inverse correlation between "not supported" sentiments and the topic "inflammatory" in the dominance analysis. This means that studies dealing with inflammation in the context of cannabis report significantly fewer negative results. This evidence base justifies the assumption that medical cannabis not only alleviates symptoms but can also take on a protective function at the pathophysiological level.

What role does cannabis play in pain management in cancer therapy?

Pain is one of the most common and burdensome symptoms in cancer patients, especially in the advanced stages of the disease. Opioids are considered the gold standard in pain therapy but are associated with significant side effects and addiction potential. Here, medical cannabis offers a promising alternative or supplement.

The meta-analysis records one of the strongest positive correlations with supportive sentiments for the topic "Pain" in the entire study. The correlation value of 0.156 (p < 7.53 × 10⁻⁵⁹) in the keyword occurrence analysis, as well as a similarly high value in the dominance analysis, indicate a pronounced scientific consensus. Studies report that cannabinoids act on the nociceptive system, especially through the activation of CB1 receptors in the central nervous system, which leads to a reduction in pain sensations.

Another advantage of medical cannabis is the possibility to reduce the use of opioids. Individual studies point out that patients using cannabis medication less frequently require high doses of opioids, which can reduce the risk of side effects and dependency. Although further research is needed on this interaction, the meta-analysis shows that the majority of studies report a positive effect on pain management.

It is also noteworthy that negative reports are rare: only a small portion of studies addressed unwanted effects such as paranoia or nervousness, and even these mostly occurred in moderate form. This underlines the good tolerability of cannabis in pain therapy for oncology patients.

How is cannabis used as a supportive treatment during chemotherapy?

Chemotherapy remains one of the central pillars of cancer treatment but is often associated with severe side effects. These mainly include nausea, vomiting, loss of appetite, and fatigue. Medical cannabis has established itself as one of the most effective complementary measures to alleviate these side effects and improve quality of life during treatment.

In the meta-analysis, the topic "Chemotherapy" showed a very strong association with supportive sentiments. The correlation value was 0.088 (p < 1.33 × 10⁻¹⁹), indicating a clear and robust evidence base. Cannabis is particularly frequently used to relieve chemotherapy-induced nausea (CINV). THC acts here via CB1 receptors in the brain, which are responsible, among other things, for regulating nausea and appetite. CBD appears to modulate the effect of THC and can enhance the anxiolytic effects.

Furthermore, there is evidence that patients who use cannabis alongside chemotherapy tolerate the treatment better and less often discontinue it. This may also have psychosomatic reasons, as cannabis positively influences not only physical well-being but also mood, sleep quality, and general resilience.

The analysis also highlights that supportive statements about cannabis use in connection with chemotherapy occur significantly more often than rejecting or unclear assessments. The dominance analysis also shows a clear trend: studies on chemotherapy and cannabis are highly likely to report positive effects. This underlines the clinical benefit as a palliative adjunct in standard oncological therapy.

Does cannabis have cancer-fighting properties?

The potentially cancer-fighting effect of cannabis is one of the most exciting and at the same time controversial fields of research in oncology. The meta-analysis by Castle et al. (2025) confirms that an increasing number of preclinical and some clinical studies provide evidence that certain cannabinoids – especially THC and CBD – can directly affect the growth of tumour cells.

The analysed data show that the topic "Anticarcinogenic" has a highly significant association with supportive sentiments, with a correlation value of 0.088 (p < 7.17 × 10⁻²⁰). The studies examined describe, among other things, that cannabinoids induce apoptosis (programmed cell death of cancer cells), inhibit angiogenesis (the formation of new blood vessels that supply tumours with nutrients), and block signalling pathways crucial for the growth of malignant cells.

The picture is particularly nuanced for different types of cancer: certain breast cancer subtypes seem sensitive to THC- or CBD-containing therapies, while other tumours such as glioblastomas, pancreatic cancers, or prostate cancer involve different receptor profiles. The so-called "entourage effect" – the synergistic effect of several cannabinoids and terpenes – is also increasingly regarded as therapeutically relevant.

However, the meta-analysis also emphasises that many of these effects have so far been demonstrated mainly in vitro or in animal studies. Clinically reliable data in humans are scarce and urgently needed. Nevertheless, the quantitative evaluation shows that the scientific community increasingly recognises the cancer-fighting potentials of cannabis – without becoming uncritical.

How is cannabis used to increase appetite during cancer treatments?

Loss of appetite and unwanted weight loss are common accompanying symptoms of cancer, especially during chemotherapy. The so-called "anorexia-cachexia syndrome" can significantly worsen the prognosis. Medical cannabis is used here because, through its effect on the endocannabinoid system, it can modulate essential bodily functions such as hunger and metabolism.

The meta-analysis assigns the topic "Appetite" a correlation value of 0.066 (p < 5.91 × 10⁻¹²) – a clear indication of a consistent positive study situation. THC activates CB1 receptors in the hypothalamus, thereby stimulating the feeling of hunger. CBD also seems to support this, especially by modulating serotonergic and dopaminergic systems that influence eating behaviour.

Many patients report a noticeable increase in appetite and weight stabilization in clinical studies. Although there are some studies with inconsistent results – depending on cancer type, dosage, or individual reaction – the sentiment analysis shows a clear majority of positive assessments.

Notably, the dominance analysis found no significant "not supported" or "unclear" results. This underlines the clinical relevance and potential standardisation of cannabis as a supportive measure to promote appetite in cancer patients.

How is cannabis used to relieve nausea caused by chemotherapy?

Chemotherapy-induced nausea and vomiting (CINV) are among the most distressing side effects for cancer patients. Even modern anti-nausea drugs often do not fully suppress these complaints. Cannabis has been used in this context since the 1980s – partly in synthetic form (e.g., dronabinol), partly as an extract.

The current meta-analysis confirms this tradition with impressive statistical clarity: the topic "Nausea" shows a correlation of 0.079 (p < 2.95 × 10⁻¹⁶), indicating a stable evidence base. Cannabinoids act via CB1 receptors in the brainstem, where they influence the neural pathways that trigger nausea and vomiting.

Subjective patient reports also confirm these results. Many state that they feel significantly better through cannabis treatment, suffer less vomiting, and thus improve treatment adherence. The analysis also notes that both the keyword-based and dominant sentiment analyses show no significant negative results – a strong indication of acceptance and effectiveness in practice.

How does cannabis affect tumour growth and tumour size?

A central goal of modern oncology is not only symptom control but also the direct inhibition of tumour growth. This raises the question of whether cannabis, beyond its immune-modulating and cell-regulating effects, also acts to inhibit tumours. The meta-analysis addresses this question using the categories "Tumor growth" and "Tumor size."

Both topics show significant positive correlations with supportive study results. "Tumor growth," for example, has a correlation value of 0.037 (p < 0.0001), and "Tumor size" 0.022 (p < 0.025). These figures indicate growing evidence that cannabinoids can inhibit the proliferation of tumour cells and slow the growth of existing tumours in preclinical models.

This is explained mechanistically by various effects: inhibition of cell cycle progression, induction of self-digestion (autophagy), influence on gene expression of oncogenic signalling pathways, and an anti-inflammatory microenvironment that hinders tumour growth. Inhibition of tumour angiogenesis also plays a role, as it reduces the tumour's nutrient supply.

However, it should be noted that these findings mainly come from animal models and cell culture studies. Clinical studies in humans are still pending. Nevertheless, the dominant sentiment analyses show a stable pattern in favour of a supportive effect, while opposing statements hardly occur significantly.

What does research show about the long-term effects of cannabis use in cancer treatment?

The long-term effects of medical cannabis use in cancer patients have so far been only limitedly studied. The meta-analysis addresses this mainly in the context of sentiment distribution across the entire body of literature. Here, an impressively consistent tendency in favour of supportive statements is evident – both regarding acute effects and longer-term observations.

Of a total of 10,641 analysed studies, over 71% were characterised by a supportive sentiment. The likelihood that a study describes a supportive effect of cannabis was more than 31 times higher than the opposite. This speaks for a consistent positive assessment – also taking into account potential limitations such as publication bias or heterogeneity of studies.

At the same time, the analysis emphasises the need for further research to systematically capture long-term effects – especially regarding mental health, risks of dependency, and interactions with other medicines. Currently, there is no evidence of serious long-term harm in the oncological context, but the evidence base in this regard is still expandable.