5477 Males and 1534 Females, Death from Cannabis, 7011 Deaths, USA, 1999-2015 - There goes the "Nobody ever died from cannabis myth"

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Brain scans of nearly 1,000 past and present marijuana users revealed abnormally low blood flow throughout their brains, compared with a smaller control group of 92 people who'd never used pot.

"The differences were astonishing," said lead researcher Dr. Daniel Amen, a psychiatrist and founder of the U.S.-based Amen Clinics. "Virtually every area of the brain we measured was lower in blood flow and activity in the marijuana smokers than in the healthy group." Blood flow was lowest in the hippocampus of marijuana users, which Amen found most troubling.

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Ian Johnston, Science Correspondent, Friday 9 December

Research could ‘highlight the neurotoxic effects of cannabis use on the central nervous system as a result of how it affects retinal processing’
Marijuana may have neurotoxic effects, researchers have found. Regularly smoking cannabis may damage users’ eyesight by triggering an abnormality in the retina, a new study has found.

Researchers in France tested 28 cannabis smokers and 24 people who did not use the drug to see how well their retinal cells responded to electrical signals.

A small but significant delay was found in the time taken for the signals to be processed by the retina of the marijuana users by comparison with the control group.

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by Kayt Sukel December 6, 2016

California’s Proposition 64, or the Adult Use of Marijuana Act, passed on Nov. 8, 2016, making it legal for people 21 and older in that state to use marijuana recreationally. California is just the latest—more than 20 states have now legalized some manner of Cannabis sativa use and it is expected that more will follow. At Neuroscience 2016, the annual meeting of the Society for Neuroscience, Nora Volkow, director of the National Institute of Drug Abuse, said these changes in legislation are cause for concern…“With the changes in legislation, we are already seeing an increase in consumption of marijuana across the population of the United States,” said Volkow…

That impact appears to be significant. In a talk entitled, “Translational Neuroepigenetic Insights of Addiction Vulnerability,” Hurd discussed how her research is demonstrating that both adolescent marijuana use, as well as exposure to THC in utero, makes epigenetic changes to the brain, priming it for greater susceptibility for later addiction to opiate drugs.
“We see specific morphological changes in the brain to important neurotransmitter systems, and individuals who are exposed to THC early in life show greater sensitivity to opiates than others do,” she said. “We know that the brain definitely adapts to marijuana. It is profoundly changing the receptors and receptor signaling that impact gene expression. And the changes it makes last through adulthood and even into the next generation.

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1. Madeline H. Meiera,b,1, 2. Avshalom Caspia,b,c,d,e, 3. Antony Amblere,f,  4. HonaLee Harringtonb,c,d, 5. Renate Houtsb,c,d, 6. Richard S. E. Keefed, 7. Kay McDonaldf, 8. Aimee Wardf, 9. Richie Poultonf, and 10. Terrie E. Moffitta,b,c,d,e

1. aDuke Transdisciplinary Prevention Research Center, Center for Child and Family Policy,
2. bDepartment of Psychology and Neuroscience, and
3. cInstitute for Genome Sciences and Policy, Duke University, Durham, NC 27708;
4. dDepartment of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710;
5. eSocial, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College London, London SE5 8AF, United Kingdom; and
6. fDunedin Multidisciplinary Health and Development Research Unit, Department of Preventive and Social Medicine, School of Medicine, University of Otago, Dunedin 9054, New Zealand
1. Edited by Michael I. Posner, University of Oregon, Eugene, OR, and approved July 30, 2012 (received for review April 23, 2012)

Abstract
Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users. Participants were members of the Dunedin Study, a prospective study of a birth cohort of 1,037 individuals followed from birth (1972/1973) to age 38 y. Cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 y. Neuropsychological testing was conducted at age 13 y, before initiation of cannabis use, and again at age 38 y, after a pattern of persistent cannabis use had developed. Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.