Neuropsychopharmacology - Abstract of article: Functional Connectivity in Brain Networks Underlying Cognitive Control in Chronic Cannabis Users

Once again we see no harm to the brain from regular marijuana use, in fact this study presents evidence that connectivity in the brain is enhanced by long-term, chronic marijuana smoking. Unfortunately, hobbled by euphoranoia and marijuanaphobia, the authors speculate that these improvements in brain structure result from compensatory actions resulting from impairment by euphoria when in reality the improvement in brain structure is more likely the result of direct actions triggered by cannabinoids, especially THC. We know that THC has the amazing ability to stimulate the production of healthy new brain cells, a process known as neurogenesis, therefore it is not unreasonable to speculate that the improved connections in the brain result from the positive biochemical effects of this neuroprotective, neuroreparative cannabinoid. The powerful stigma associated with marijuana that was brainwashed into two generations with reefer madness campaigns supported by reams of pseudo-scientific data continues to blind researchers to the reality that cannabinoids are health-building and health-regulating compounds and that supplementing our naturally-produced supply of these vital compounds with cannabis or cannabis products vastly improves all aspects of human health. Functional Connectivity in Brain Networks Underlying Cognitive Control in Chronic Cannabis Users

Ian H Harding1, Nadia Solowij2,3, Ben J Harrison1, Michael Takagi1, Valentina Lorenzetti1, Dan I Lubman4, Marc L Seal5,6, Christos Pantelis1 and Murat Yücel1

1Department of Psychiatry, Melbourne Neuropsychiatry Centre, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia

2School of Psychology, University of Wollongong, Wollongong, NSW, Australia

3Schizophrenia Research Institute, Sydney, NSW, Australia

4Turning Point Alcohol and Drug Centre, Eastern Health and Monash University, Melbourne, VIC, Australia

5Murdoch Childrens Research Institute, Melbourne, VIC, Australia

6Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia

Correspondence: Dr IH Harding and Professor M Yücel, Department of Psychiatry, Melbourne Neuropsychiatry Centre, Alan Gilbert Building, University of Melbourne, 3/161 Barry Street, Carlton, Melbourne, VIC 3053, Australia, Tel: (+61 3) 8344 1861, Fax: (+61 3) 9348 0469, E-mail: and

Received 21 September 2011; Revised 13 February 2012; Accepted 1 March 2012

Advance online publication 25 April 2012

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The long-term effect of regular cannabis use on brain function underlying cognitive control remains equivocal. Cognitive control abilities are thought to have a major role in everyday functioning, and their dysfunction has been implicated in the maintenance of maladaptive drug-taking patterns. In this study, the Multi-Source Interference Task was employed alongside functional magnetic resonance imaging and psychophysiological interaction methods to investigate functional interactions between brain regions underlying cognitive control. Current cannabis users with a history of greater than 10 years of daily or near-daily cannabis smoking (n=21) were compared with age, gender, and IQ-matched non-using controls (n=21). No differences in behavioral performance or magnitude of task-related brain activations were evident between the groups. However, greater connectivity between the prefrontal cortex and the occipitoparietal cortex was evident in cannabis users, as compared with controls, as cognitive control demands increased. The magnitude of this connectivity was positively associated with age of onset and lifetime exposure to cannabis. These findings suggest that brain regions responsible for coordinating behavioral control have an increased influence on the direction and switching of attention in cannabis users, and that these changes may have a compensatory role in mitigating cannabis-related impairments in cognitive control or perceptual processes.


attention; brain; cannabis; cognitive control; functional connectivity

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