Persistent cannabis users show neuropsychological decline from childhood to midlife:
My commentary:
The studies just keep coming which show damage done by using pot.
Though most users remain in denial, we are thankful to those who volunteer to participate in legitimate studies rather than those done with an agenda other than life/safety issues – by those who cannot see beyond their own agenda to get high and to drag others into their lifestyle.
As more questions arise, the hope is, that users will discontinue promoting it as medicinal and looking the other way, which for them, their offspring, and loved ones leaves scientific facts lingering in the shadows. 
1. Madeline H. Meiera,b,1, 2. Avshalom Caspia,b,c,d,e, 3. Antony Amblere,f, 4. HonaLee Harrington,b,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
+ Author Affiliations
1) (a) Duke Transdisciplinary Prevention Research Center, Center for Child and Family Policy,
2) (b) Department of Psychology and Neuroscience, and
3) (c) Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708;
4. (d) Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710;
5. (e) Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College London, London SE5 8AF, United Kingdom; and
6. (f) Dunedin 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.
