The strongest evidence regarding cannabis and memory focuses on its temporary negative effects on short-term and working memory.In a 2001 study looking at 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". On his studies regarding cannabis use, lead researcher and Harvard professor Harrison Pope said he found marijuana is not dangerous over the long term, but there are short-term effects. From neuropsychological tests, Pope found that chronic cannabis users showed difficulties, 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". Researchers from the University of California, San Diego School of Medicine failed to show substantial, systemic neurological effects from long-term recreational use of cannabis. Their findings were published in the July 2003 issue of the Journal of the International Neuropsychological Society. The research team, headed by Dr Igor Grant, found that cannabis use did affect perception, but did 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 the memory and learning. Other functions such as reaction time, attention, language, reasoning ability, perceptual and motor skills were unaffected.
Cytokine receptor-like factor 1 is a protein that in humans is encoded by the CRLF1 gene. Function
This gene encodes a member of the cytokine type I receptor family. The protein forms a secreted complex with cardiotrophin-like cytokine factor 1 and acts on cells expressing ciliary neurotrophic factor receptors. The complex can promote survival of neuronal cells. Clinical significance
Mutations in this gene are associated with two conditions, both rare:

Cold-induced sweating syndrome, characterized by profuse hyperhidrosis in cold environmental temperature and characteristic craniofacial and skeletal features)
Crisponi syndrome (CS), characterized by neonatal-onset paroxysmal muscular contractions, abnormal function of the autonomic nervous system and craniofacial and skeletal manifestations such as thick and arched eyebrows, a short nose with anteverted nostrils, full cheeks, an inverted upper lip and a small mouth.It is unknown whether the two conditions are distinct clinical entities or a single clinical entity with variable expressions. Other characteristic features in CRLF1 mutation include marfanoid habitus with progressive kyphoscoliosis and craniofacial characteristics including dolichocephaly, a slender face with poor expression, a nose with hypoplastic nares, malar hypoplasia and prognathism. References
Further reading
External links
GeneReviews/NCBI/NIH/UW entry on Cold-Induced Sweating Syndrome including Crisponi Syndrome
OMIM enries on Cold-Induced Sweating Syndrome including Crisponi Syndrome
Human CRLF1 genome location and CRLF1 gene details page  in the UCSC Genome Browser.This article incorporates text from the United States National Library of Medicine, which is in the public domain.