A growing number of RCTs, meta-analyses as well as observational studies in clinical practice demonstrate the efficacy of medicinal cannabis for chronic pain. According to meta-analysis of eight studies from 2015, the use of medicinal cannabis resulted in at least a 30 percent reduction in chronic pain compared to placebo.1. Cannabis also showed improvement in quality of life.2,3. Further studies show that the use of medicinal cannabis allowed to reduce co-medication of opioids and NSAIDs.4,2
Twelve randomized controlled trials have shown that the use of medicinal cannabis as an adjunctive therapy in multiple sclerosis (MS) significantly alleviates several symptoms.1 These include a reduction in spasticity5,6 associated pain7, and an improvement in quality of sleep.5,8
According to various cohort studies and RCT's, medicinal cannabis can help to improve the quality of life of women with endometriosis based on its anti-inflammatory and analgesic effects.9,10 In an Australian survey from 2017, women with endometriosis confirmed a reduction in pain and other symptoms when using cannabis11. In particular, they reported improvements in sleep, nausea and vomiting. A Canadian study conducted between 2017 and 202012 also concluded that cannabis appears to be effective for pelvic pain, gastrointestinal problems, and mood.
Recent studies indicate efficacy of medicinal cannabis for various symptoms of fibromyalgia, namely physical symptoms such as muscle stiffness but also neurological and psychological symptoms13. This demonstrated that some of the main symptoms such as pain, insomnia and depressiveness can improve when treated with medicinal cannabis. For example, scientists at the Clinical Cannabis Research Institute in Israel analysed data from fibromyalgia patients between 2015 and 2017 in a prospective observational study.14 The result: 81 percent of study participants noted a positive effect from cannabinoid therapy. Among others, the pain intensity of participating patients* had decreased from an average from 9 (on a pain scale of 1 to 10) to 5 at the end of the observation period.
A study published in 2020 also found that nearly half of patients (47 percent) were able to forgo any other therapy during treatment with cannabis-based medicines.15 The average improvement in sleep and pain was just over 77 percent.
Research on the topic of cannabis and ADHD is still in its infancy. Very few and small studies are available so far, but they are cautiously optimistic. A 2017 study at King's College in London illustrates the need for further research into the links between ADHD and symptom improvement with cannabis. According to the researchers, this study provides "preliminary evidence supporting the self-medication theory of cannabis use in ADHD and the need for further studies of the endocannabinoid system in ADHD."16 This contrasts with various case reports from patients, treating physicians, and clinicians. Many adult ADHD patients report that cannabis therapy helps them better adjust to everyday life because the treatment makes them more focused, calm, and concentrated. It also has positive effects on problems such as insomnia, depression, and impulsive behavior.
For tumor-related pain, the use of cannabis-based medications (nabiximol) is recommended as adjuvant therapy when opioids or other established analgesics have previously failed to adequately relieve pain.17 RCTs conducted to date demonstrate a positive effect of medicinal cannabis on the relief of tumor-related pain. Two studies demonstrated that patients receiving cannabis-based therapy more frequently achieved a clinically relevant pain reduction of 30 percent.18,19 In 2010, Johnson et al. showed that 43 percent of patients treated with a THC/CBD extract achieved a 30 percent pain reduction, more than twice as many as in the placebo group (21 percent).18 In addition, two studies showed significant improvement in sleep quality of tumor patients.19,20
A meta-analysis of three recent RCTs reported a significant positive effect of cannabis medicines compared to placebo on chemotherapy-induced nausea and vomiting.1 Another study comparing the effect of THC with the first-line antiemetic treatment ondansetron demonstrated equivalent symptom relief to ondansetron. Symptom relief with THC: 57 to 58 percent of patients treated with either THC or ondansetron reported complete absence of nausea and vomiting.21
1 Whiting, P. F. et al. Cannabinoids for medical use: A systematic review and meta-analysis. JAMA – J. Am. Med. Assoc. 313, 2456–2473 (2015).
2 Bellnier, T., Brown, G. W. & Ortega, T. R. Preliminary evaluation of the efficacy, safety, and costs associated with the treatment of chronic pain with medical cannabis. Ment. Heal. Clin. 8, 110–115 (2018).
3 Ware, M. A., Wang, T., Shapiro, S. & Collet, J. P. Cannabis for the Management of Pain: Assessment of Safety Study (COMPASS). J. Pain 16, 1233–1242 (2015). Bellnier, T., Brown, G. W. & Ortega, T. R. Preliminary evaluation of the efficacy, safety, and costs associated with the treatment of chronic pain with medical cannabis. Ment. Heal. Clin. 8, 110–115 (2018).
4 Ware, M. A., Wang, T., Shapiro, S. & Collet, J. P. Cannabis for the Management of Pain: Assessment of Safety Study (COMPASS). J. Pain 16, 1233–1242 (2015).
5 Assessment of Safety Study (COMPASS). J. Pain 16, 1233–1242 (2015). rallel-group, enriched-design study of nabiximols* (Sativex®), as add-on therapy, in subjects with refractory spasticity caused by multiple sclerosis. Eur. J. Neurol. 18, 1122–1131 (2011).
6 Corey-Bloom, J. et al. Smoked cannabis for spasticity in multiple sclerosis: A randomized, placebo-controlled trial. CMAJ 184, 1143–1150 (2012).
7 Schimrigk, S. et al. Dronabinol Is a Safe Long-Term Treatment Option for Neuropathic Pain Patients. Eur. Neurol. 78, 320–329 (2017).
8 Zajicek, J. P., Hobart, J. C., Slade, A., Barnes, D. & Mattison, P. G. Multiple sclerosis and extract of cannabis: Results of the MUSEC trial. J. Neurol. Neurosurg. Psychiatry 83, 1125–1132 (2012).
9 Liang AL et al. Medical Cannabis for Gynecologic Pain Conditions: A Systematic Review. Obstet Gynecol. 139(2): 287 - 296 (2022). REVIEW.
10 Jerome Bouaziz,1,2,*Alexandra Bar On,1,2Daniel S. Seidman,1,2and David Soriano. The Clinical Significance of Endocannabinoidsin Endometriosis Pain Management. Cnnabis and Cannabinoid Research 2(1)
11 Sinclair, J., Smith, C. A., Abbott, J., Chalmers, K. J., Pate, D. W., & Armour, M. (2020). Cannabis use, a self-management strategy among Australian women with endometriosis: results from a national online survey. Journal of Obstetrics and Gynaecology Canada, 42(3), 256-261.
12 Sinclair, J., Collett, L., Abbott, J., Pate, D. W., Sarris, J., & Armour, M. (2021). Effects of cannabis ingestion on endometriosis-associated pelvic pain and related symptoms. PloS one, 16(10), Online Version.
13 Yassin M. et al. Effect of adding medical cannabis treatment (MCT) to analgesic treatment in patients with low back pain related to fibromyalgia: an observational cross-over single center study Clin Exp Rheumatol. 37 Suppl 116(1):13-20. (2019).
14 Sagy I et al. Safety and Efficacy of Medical Cannabis in Fibromyalgia. J. Clin. Med. 8, 807 (2019).
15 Habib, G. und Levinger, U. Characteristics Of Medical Cannabis Usage Among Patients With Fibromyalgia Harefuah 159(5):343-348 (2020).
16 Cooper R.E., Williams E., Seegobin S., Tye C., Kuntsi J., Asherson P.: Cannabinoids in attention-deficit/hyperactivity disorder: a randomised-controlled trial. Eur Neuropsychopharmacol 2017;27(8):795–808.
17 Häuser, W. et al. European Pain Federation (EFIC) position paper on appropriate use of cannabis-based medicines and medical cannabis for chronic pain management. Eur. J. Pain (United Kingdom) 22, 1547–1564 (2018).
18 Johnson, J. R. et al. Multicenter, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study of the Efficacy, Safety, and Tolerability of THC:CBD Extract and THC Extract in Patients with Intractable Cancer-Related Pain. J. Pain Symptom Manage. 39, 167–179 (2010).
19 Portenoy, R. K. et al. Nabiximols for opioid-treated cancer patients with poorly-controlled chronic pain: A randomized, placebo-controlled, graded-dose trial. J. Pain 13, (2012).
20 Lichtman, A. H. et al. Results of a Double-Blind, Randomized, Placebo-Controlled Study of Nabiximols Oromucosal Spray as an Adjunctive Therapy in Advanced Cancer Patients with Chronic Uncontrolled Pain. J. Pain Symptom Manage. 55, 179–188.e1 (2018).
21 Meiri, E. et al. Efficacy of dronabinol alone and in combination with ondansetron versus ondansetron alone for delayed chemotherapy-induced nausea and vomiting. Curr. Med. Res. Opin. 23, (2007).