Editing Effects of cannabis (section)

===Memory and learning===
{{main|Cannabis and memory}}
Studies on cannabis and memory are hindered by small sample sizes, confounding drug use, and other factors.<ref name= "memory_hindered" >{{cite book | vauthors = Riedel G, Davies SN | chapter = Cannabinoid function in learning, memory and plasticity | volume = 168 | issue = 168 | pages = 445–77 | year = 2005 | pmid = 16596784 | doi = 10.1007/3-540-26573-2_15 | isbn = 978-3-540-22565-2 | series = Handbook of Experimental Pharmacology | title = Cannabinoids }}</ref> The strongest evidence regarding cannabis and memory focuses on its temporary negative effects on short-term and working memory.<ref name= "memory_hindered" />

In a 2001 study of neuropsychological performance in long-term cannabis users, researchers found "some cognitive deficits appear detectable at least 7 days after heavy cannabis use but appear reversible and related to recent cannabis exposure rather than irreversible and related to cumulative lifetime use".<ref>{{cite journal | vauthors = Pope HG, Gruber AJ, Hudson JI, Huestis MA, Yurgelun-Todd D | title = Neuropsychological performance in long-term cannabis users | journal = Archives of General Psychiatry | volume = 58 | issue = 10 | pages = 909–15 | date = October 2001 | pmid = 11576028 | doi = 10.1001/archpsyc.58.10.909 | doi-access =  }}</ref> Of his studies on cannabis use, lead researcher and Harvard professor [[Harrison Pope]] said he found it is not dangerous over the long term, but there are short-term effects. From neuropsychological tests, Pope found that chronic cannabis users showed difficulty with verbal memory in particular for "at least a week or two" after they stopped smoking. Within 28 days, memory problems vanished and the subjects "were no longer distinguishable from the comparison group".<ref>Lyons, Casey (October 2012) [http://www.bostonmagazine.com/2012/09/medical-marijuana-in-massachusetts/5 "Lost in the Weeds: Legalizing Medical Marijuana in Massachusetts"] {{Webarchive|url=https://web.archive.org/web/20141024181655/http://www.bostonmagazine.com/2012/09/medical-marijuana-in-massachusetts/5 |date=24 October 2014 }}. ''[[Boston (magazine)|Boston]]''.</ref>
Researchers at the [[University of California, San Diego School of Medicine]] failed to show substantial, systemic neurological effects from long-term cannabis use. Their findings were published in the July 2003 issue of the ''Journal of the International Neuropsychological Society''.<ref>[https://web.archive.org/web/20130314031728/http://health.ucsd.edu/news/2003/06_27_Grant.html Minimal Long-Term Effects of Marijuana Use Found]. ''Journal of the International Neuropsychological Society'' (27 June 2003)</ref> The research team, headed by Igor Grant, found that cannabis use affects perception but does not cause permanent [[brain damage]]. Researchers looked at data from 15 previously published controlled studies involving 704 long-term cannabis users and 484 nonusers. The results showed long-term cannabis use was only marginally harmful on memory and learning. Other functions such as reaction time, attention, language, reasoning ability, and perceptual and motor skills were unaffected. The observed effects on memory and learning, they said, showed long-term cannabis use caused "selective memory defects", but "of a very small magnitude".<ref>Beasley, Deena (27 June 2003) [https://web.archive.org/web/20150306045312/http://www.cmcr.ucsd.edu/images/pdfs/Reuters_062703.pdf Study – Pot doesn't cause permanent brain damage]. ''Reuters Health E-Line''</ref> A study by [[Johns Hopkins University School of Medicine]] found that heavy cannabis use is associated with decrements in neurocognitive performance even after 28 days of abstinence.<ref>{{cite journal | vauthors = Bolla KI, Brown K, Eldreth D, Tate K, Cadet JL | s2cid = 11525660 | title = Dose-related neurocognitive effects of marijuana use | journal = Neurology | volume = 59 | issue = 9 | pages = 1337–43 | date = November 2002 | pmid = 12427880 | doi = 10.1212/01.WNL.0000031422.66442.49 }}</ref>