There is currently very little high level evidence to support the usage of medical marijuana for most currently used indications

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Migraine HA-  File 1 here

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Neuropathic pain- inconsistent findings of four systematic reviews on the efficacy of cannabis-based medicines in neuropathic pain (https://www.ncbi.nlm.nih.gov/pubmed/29034533).  Another review found neuropathic pain (compared with placebo), there was evidence of a small effect; however, confidence in the estimate is low and these results could not be considered conclusive.(https://www.ncbi.nlm.nih.gov/pubmed/29119763).  There is limited evidence for a benefit of THC/CBD spray in the treatment of neuropathic pain. (https://www.ncbi.nlm.nih.gov/pubmed/29017688)   Another review concluded from 27 chronic pain trials, there is low-strength evidence that cannabis alleviates neuropathic pain (https://www.ncbi.nlm.nih.gov/pubmed/28806817).  Another review found cannabinoids were marginally superior to placebo in terms of efficacy and inferior in terms of tolerability. (https://www.ncbi.nlm.nih.gov/pubmed/26830780)

Chronic pain- found for chronic (compared with placebo), there was evidence of a small effect; however, confidence in the estimate is low and these results could not be considered conclusive.(https://www.ncbi.nlm.nih.gov/pubmed/29119763).  Another review found there was moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain and spasticity. (https://www.ncbi.nlm.nih.gov/pubmed/26103030)

Multiple Sclerosis- Inconsistent findings in one systematic review for painful spasms in multiple sclerosis (https://www.ncbi.nlm.nih.gov/pubmed/29034533).  Another review found the efficacy of cannabis (compared with placebo) in patients with multiple sclerosis, confidence in the estimate was high in favour of cannabis for spasticity (numerical rating scale and visual analogue scale, but not the Ashworth scale) and pain (https://www.ncbi.nlm.nih.gov/pubmed/29119763).  Another review found no definitive conclusions can be made about the efficacy of cannabinoid medication due to conflicting results across three studies (https://www.ncbi.nlm.nih.gov/pubmed/28376639)

Rheumatoid arthritis - There were consistent results that there was insufficient evidence of any cannabis-based medicine for pain management in patients with rheumatic diseases in three Systematic Reviews (https://www.ncbi.nlm.nih.gov/pubmed/29034533).  Another review found there is inadequate evidence for any benefit of cannabinoids (dronabinol, nabilone, medical cannabis, or THC/CBD spray) to treat pain of rheumatic origin (https://www.ncbi.nlm.nih.gov/pubmed/29017688)

Cancer pain- There were consistent results that there was insufficient evidence of any cannabis-based medicine for pain management in patients with cancer pain in two systematic reviews  (https://www.ncbi.nlm.nih.gov/pubmed/29034533).  There is uncertainty whether cannabis, including extracts and tinctures, compared with placebo or other antiemetic drugs reduces nausea and vomiting in patients with cancer requiring chemotherapy, although the confidence in the estimate of the effect was low or very low. (https://www.ncbi.nlm.nih.gov/pubmed/29119763)   Another review found there is inadequate evidence for any benefit of cannabinoids (dronabinol, nabilone, medical cannabis, or THC/CBD spray) to treat cancer pain or anorexia in cancer (https://www.ncbi.nlm.nih.gov/pubmed/29017688). 

AIDS -  There is inadequate evidence for any benefit of cannabinoids (dronabinol, nabilone, medical cannabis, or THC/CBD spray) to treat AIDS. (https://www.ncbi.nlm.nih.gov/pubmed/29017688)

PTSD - Evidence is insufficient to draw conclusions about the benefits and harms of plant-based cannabis preparations in patients with PTSD (https://www.ncbi.nlm.nih.gov/pubmed/28806794). 

Chemotherapy induced nausea and vomiting (CINV) - There was moderate quality evidence on the efficacy of cannabis or derived medications (CBs) compared to placebo and conventional antiemetics for CINV. There was moderate quality evidence that pharmaceutical CBs were less tolerated and less safe than placebo and conventional antiemetics in CINV. (https://www.ncbi.nlm.nih.gov/pubmed/26787227).  Another review showed there was low-quality evidence suggesting that cannabinoids were associated with improvements in nausea and vomiting due to chemotherapy (https://www.ncbi.nlm.nih.gov/pubmed/26103030)

HIV - There was low-quality evidence suggesting that cannabinoids were associated with improvements in  weight gain in HIV infection (https://www.ncbi.nlm.nih.gov/pubmed/26103030)

Sleep disorders- There was low-quality evidence suggesting that cannabinoids were associated with improvements in sleep disorders. (https://www.ncbi.nlm.nih.gov/pubmed/26103030)

Tourette Syndrome- There was low-quality evidence suggesting that cannabinoids were associated with improvements in Tourette syndrome. (https://www.ncbi.nlm.nih.gov/pubmed/26103030)

Epilepsy - No reliable conclusions can be drawn at present regarding the efficacy of cannabinoids as a treatment for epilepsy. The dose of 200 to 300 mg daily of cannabidiol was safely administered to small numbers of patients generally for short periods of time (https://www.ncbi.nlm.nih.gov/pubmed/245954910)

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Marijuana Harms:  Systematic Reviews 

One systematic review found harms in general population include increased risk for motor vehicle accidents, psychotic symptoms, and short-term cognitive impairment (https://www.ncbi.nlm.nih.gov/pubmed/28806817).  A systematic review of acute pancreatitis demonstrated cannabis is a possible risk factor for acute pancreatitis (AP) and recurrent AP, occurring primarily in young patients under the age of 35 years (https://www.ncbi.nlm.nih.gov/pubmed/28796137). 

 

In a case-crossover self-report study a significant odds ratio increase was found for driving- related injury after combined exposure to cannabis and alcohol compared to cannabis alone (OR of 10.9 and 5.8 respectively). Both, experimental and epidemiological studies have revealed that THC affects negatively both, psychomotor skills and cognitive functions. Studies of the acute effects of cannabis on driving have shown that drivers under the influence of this substance are impaired. Indeed, driving under the influence of cannabis doubles or triples the risk of a crash. Specifically, cannabis use impairs critical-tracking tasks, increases lane weaving, decreases reaction time, and divided attention. (https://www.ncbi.nlm.nih.gov/pubmed/28440193)

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Hyperemesis syndrome diagnostic criteria: history of regular cannabis for any duration of time (100%), cyclic nausea and vomiting (100%), resolution of symptoms after stopping cannabis (96.8%), compulsive hot baths with symptom relief (92.3%), male predominance (72.9%), abdominal pain (85.1%), and at least weekly cannabis use (97.4%). (https://www.ncbi.nlm.nih.gov/pubmed/28000146)

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Maternal marijuana use during pregnancy is not an independent risk factor for adverse neonatal outcomes after adjusting for confounding factors. Thus, the association between maternal marijuana use and adverse outcomes appears attributable to concomitant tobacco use and other confounding factors  (https://www.ncbi.nlm.nih.gov/pubmed/27607879)

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There was an increased risk of short-term AEs with cannabinoids, including serious AEs. Common AEs included dizziness, dry mouth, nausea, fatigue, somnolence, euphoria, vomiting, disorientation, drowsiness, confusion, loss of balance, and hallucination.(https://www.ncbi.nlm.nih.gov/pubmed/26103030)

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Findings whilst tentative, suggest that cannabis use may worsen the occurrence of manic symptoms in those diagnosed with bipolar disorder, and may also act as a causal risk factor in the incidence of manic symptoms. This underscores the importance of discouraging cannabis use among youth and those with bipolar disorder to help prevent chronic psychiatric morbidity. More high quality prospective studies are required to fully elucidate how cannabis use may contribute to the development of mania over time (https://www.ncbi.nlm.nih.gov/pubmed/25285897)

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In a study presented at the March 2018 American Pain Society meeting, it was shown pain scores do not decrease when using cannabis whereas sleep scores are worse despite people taking cannabis for sleep.

"We were especially surprised to find that cannabis interferes with sleep -- particularly at a higher frequency and quantity -- because that's not what patients tell us," study co-author Mary Lee Roberts, PhD, RN, also of WSU, told MedPage Today during a poster session at the American Pain Society's Scientific Summit. "They tell us that 'I do it so I can sleep,' but our findings indicate something other than that."

The analysis looked at adults who were prescribed opioids for persistent pain (n=150), as well as those who were involved in a medication-assisted treatment for opioid use disorder (n=150). Between the groups, adults with persistent pain were more likely to be older and have a higher level of education, while those with opioid use disorder were more likely to self-report a history of ever-using cannabis (92.7% versus 69.8%).

"Cannabis use is frequently reported within both populations to manage pain and sleep problems, although how cannabis influences co-occurring symptoms is uncertain," the researchers explained.

Participants' sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI), while pain intensity and self-efficacy of symptom managment were measured via the Patient-Reported Outcomes Measurement Information System. Among both groups, 87% of adult opioid users had clinically poor sleep quality (PSQI >5).

When comparing the two groups, those with persistent pain tended to have poorer quality of sleep (average PSQI 11.82 versus 9.96, P=0.001), as well as a higher level of pain intensity (58.64 versus 53.6, P<0.001), compared with those with opioid use disorder.  The study's authors include Marian Wilson, PhD, MPH, RN-BC,and Mary Lee Roberts, PhD, RN

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Guidelines for Marijuana Use

We developed 10 major recommendations for lower-risk use: (1) the most effective way to avoid cannabis use-related health risks is abstinence, (2) avoid early age initiation of cannabis use (i.e., definitively before the age of 16 years), (3) choose low-potency tetrahydrocannabinol (THC) or balanced THC-to-cannabidiol (CBD)-ratio cannabis products, (4) abstain from using synthetic cannabinoids, (5) avoid combusted cannabis inhalation and give preference to nonsmoking use methods, (6) avoid deep or other risky inhalation practices, (7) avoid high-frequency (e.g., daily or near-daily) cannabis use, (8) abstain from cannabis-impaired driving, (9) populations at higher risk for cannabis use-related health problems should avoid use altogether, and (10) avoid combining previously mentioned risk behaviors (e.g., early initiation and high-frequency) (https://www.ncbi.nlm.nih.gov/pubmed/28644037).