Hello and thank you for the great question,
(see the very last paragraph for the short answer)
While arthritis and stenosis cause different types of pain, cannabis should help alleviate both types.
Arthritis causes nociceptive pain, whereas spinal stenosis leads to neuropathic pain.
Nociceptive pain is the immediate-cause-effect pain felt when someone is injured. Nociceptors are pain receptors that detect when there is a threat to your body, which then tell your brain to respond to the threat. NSAIDs and opiates work well at treating this type of pain, because they interrupt the transmission of pain signals from the site of injury to your brain.
Neuropathic pain, on the other hand, is due to damage to the nerve itself, which causes pain signals to continually fire, even if there is no injury elsewhere. Neuropathic pain is often described as a tingling or electric feeling. If you suffer from neuropathic pain, then I’m sure you’re all too well aware that this form of pain is extremely difficult to treat.
Several studies suggest that cannabis can help alleviate the pain of arthritis (nociceptive pain). And while cannabis research has historically focused on THC, synthetic cannabinoids, or our own naturally occurring cannabinoids (endocannabinoids), there is an evergrowing body of research regarding the potential medicinal benefits of CBD. In fact, a recently published study concluded that "topical CBD application has therapeutic potential for relief of arthritis pain and inflammation"
In a study with exciting implications, researchers concluded that "CBD, through its combined immunosuppressive and anti-inflammatory actions, has a potent anti-arthritic effect" which may even "block the progression of arthritis."
However, the research regarding CBD and neuropathic pain is sparse. Although, in a study published in the British Journal of Pharmacology, researchers found that chronic administration of CBD prevented paclitaxel-induced neuropathy (PAC) (paclitaxel is a common chemotherapy agent which often causes neuropathic pain). Interestingly, they found that the cannabinoid receptors CB1 and CB2 were not involved in preventing the pain from developing. Rather, they concluded that CBD is protective against PAC-induced neurotoxicity mediated in part by the serotonin receptor system. Modulation of the serotonin receptor system is also the method that antidepressant drugs are thought to affect neuropathic pain.
However, there is a significant amount of research showing that Sativex — an oromucosal spray with 1CBD:1THC — effectively reduces neuropathic pain. In 2005, Sativex was approved in Canada for the treatment of central neuropathic pain in multiple sclerosis, and in 2007 for intractable cancer pain. Numerous randomized clinical trials have demonstrated safety and efficacy for Sativex in central and peripheral neuropathic pain, rheumatoid arthritis and cancer pain.
If you are treating arthritic back pain, high CBD strains or products would likely be a good choice. If the pain is due to spinal stenosis, some extra THC would likely be beneficial. Products/strains with higher concentrations of CBD vs THC, such as 20CBD:1THC, will lessen,or even eliminate, psychoactive effects. While products with similar levels of CBD and THC have been shown to alleviate most forms of pain, including neuropathic pain, best. So, for most people, it takes some trial and error before finding an ideal compromise.