BRAIN IMAGINGCerebellar hypoactivity in frequent marijuana usersBlock, Robert I.1,9; O'Leary, Daniel S.2; Hichwa, Richard D.3; Augustinack, Jean C.4,8; Ponto, Laura L. Boles3; Ghoneim, M M.1; Arndt, Stephan2; Ehrhardt, James C.3; Hurtig, Richard R.5; Watkins, G L.3; Hall, James A.6; Nathan, Peter E.7; Andreasen, Nancy C.2Author Information 1Department of Anesthesia, Westlawn Building, Room 5140, Iowa City, IA 52242 USA 2Department of Psychiatry, University of Iowa, Iowa City, IA 52242 USA 3Department of Radiology, University of Iowa, Iowa City, IA 52242 USA 4Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242 USA 5Department of Speech Pathology and Audiology, University of Iowa, Iowa City, IA 52242 USA 6Department of Psychology, University of Iowa, Iowa City, IA 52242 USA 7School of Social Work, University of Iowa, Iowa City, IA 52242 USA 8Present address: Alzheimer's Research Unit, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA 02129, USA. 9Corresponding author and address: Robert I. Block, Departments of Anesthesia, Westlawn Building, Room 5140, Iowa City, IA 52242 USA Acknowledgements: This research was supported by grants DA10554, NIDA, NIH and RR00059, General Clinical Research Centers Program, NCRR, NIH. Thanks to Linda Smith and Michael Daugherty for assisting in data collection. Received 30 November 1999; accepted 7 January 2000 NeuroReport: March 20, 2000 - Volume 11 - Issue 4 - p 749-753 Buy Abstract It is uncertain whether frequent marijuana use adversely affects human brain function. Using PET, regional cerebral blood flow was compared in frequent marijuana users and comparable, non-using controls after at least 26 h of monitored abstention by all subjects. Marijuana users showed substantially lower brain blood flow than controls in a large region of posterior cerebellum, indicating altered brain function in frequent marijuana users. A cerebellar locus of some chronic and acute effects of marijuana is plausible, e.g. the cerebellum has been linked to an internal timing system, and alterations of time sense are common following marijuana smoking. © 2000 Lippincott Williams & Wilkins, Inc.