Look at THC / CBD proportions. There's research [0] into CBD mitigating THC's interference with memory formation.
Also, intentionally-high-CBD strains are under development [1]:
"A high-CBD cannabis strain was developed in the 1980s by David Watson and Robert Clarke, American naturalists who founded a company called Hortapharm in Amsterdam to pursue their goal of developing plant strains for different purposes. (The day Watson and Clarke became expatriates is the day the U.S. lost its lead in the field of cannabis therapeutics.) In 1998 Hortapharm sold its seed stock to a British start-up, GW Pharmaceuticals, which has since developed a strain that expresses 97% of its cannabinoid content as CBD.
GW plans to test its high-CBD strain as a treatment for rheumatoid arthritis, inflammatory bowel diseases, psychotic disorders, and epilepsy. It is now in Phase 2 trials to determine the dose levels to use in clinical trials involving people. GW mixes its high-CBD and high-THC strains in a 1:1 ratio to make Sativex, a plant extract formulated for spraying under the tongue that has been approved in Canada and elsewhere to treat neuropathic pain associated with multiple sclerosis. CBD evidently bolsters the pain-killing effects of THC while moderating its psychoactivity."
Also, intentionally-high-CBD strains are under development [1]:
"A high-CBD cannabis strain was developed in the 1980s by David Watson and Robert Clarke, American naturalists who founded a company called Hortapharm in Amsterdam to pursue their goal of developing plant strains for different purposes. (The day Watson and Clarke became expatriates is the day the U.S. lost its lead in the field of cannabis therapeutics.) In 1998 Hortapharm sold its seed stock to a British start-up, GW Pharmaceuticals, which has since developed a strain that expresses 97% of its cannabinoid content as CBD.
GW plans to test its high-CBD strain as a treatment for rheumatoid arthritis, inflammatory bowel diseases, psychotic disorders, and epilepsy. It is now in Phase 2 trials to determine the dose levels to use in clinical trials involving people. GW mixes its high-CBD and high-THC strains in a 1:1 ratio to make Sativex, a plant extract formulated for spraying under the tongue that has been approved in Canada and elsewhere to treat neuropathic pain associated with multiple sclerosis. CBD evidently bolsters the pain-killing effects of THC while moderating its psychoactivity."
[0] http://www.nature.com/news/2010/101001/full/news.2010.508.ht...
[1] http://www.counterpunch.org/2007/07/14/who-s-afraid-of-canna...