Cognitive effects of cannabis have been reviewed (Russo et al 2002; Fride and Russo 2006), but less study has occurred in therapeutic contexts. Effects of chronic heavy recreational cannabis usage on memory abate without sequelae after a few weeks of abstinence (Pope et al 2001). Studies of components of the Halstead-Reitan battery with Sativex in neuropathic pain with allodynia have revealed no changes vs placebo (Nurmikko et al 2007), and in central neuropathic pain in MS (Rog et al 2005), 4 of 5 tests showed no significant differences. While the Selective Reminding Test did not change significantly on Sativex, placebo patients displayed unexpected improvement.
Specific city and county laws have been enacted to regulate how citizens and tourists may possess and consume marijuana. Penalties exist for driving while under the influence of marijuana. Someone driving under the influence of marijuana is considered impaired in both Colorado and Washington when five nanograms per milliliter (ng/mL) of blood or more of active THC is detected.

When used as treatment for pain, CBD has a powerful effect on neuropathic pain, which is pain of the nerves and might be caused by peripheral nerve injury or other factors. By activating CB2 receptors, CBD activates many of the pathways that ease pain, and this goes a long way towards managing long term conditions such as diabetes, MS, and fibromyalgia.