Ronald I. Herning, PhD, Warren E. Better, MS, Kimberly Tate, BS and Jean L. Cadet, MD

From the Molecular Neuropsychiatry Branch, National Institute on Drug Abuse, National Institutes of Health,Baltimore,MD.

Address correspondence and reprint requests to Dr. Ronald I. Herning, Molecular Neuropsychiatry Branch, National Institute on Drug Abuse, PO Box 5180, Baltimore, MD21224; e-mail: rherning@intra.nida.nih.gov

Objective: To determine possible effects of prolonged marijuanause on the cerebrovascular system during a month of monitoredabstinence and to assess how the intensity of current use mighthave influenced cerebrovascular perfusion in these marijuanausers.

Method: The authors recorded blood flow velocity in the anteriorand middle cerebral arteries using transcranial Doppler sonographyin three groups of marijuana users who differed in the intensityof recent use (light: n = 11; moderate: n = 23; and heavy: n= 20) and in control subjects (n = 18) to assess the natureand duration of any potential abnormalities. Blood flow velocitywas recorded within 3 days of admission and 28 to 30 days ofmonitored abstinence on an inpatient research unit in orderto evaluate subacute effects of the drug and any abstinence-generatedchanges.

Results: Pulsatility index, a measure of cerebrovascular resistance,and systolic velocity were significantly increased in the marijuanausers vs control subjects. These increases persisted in theheavy marijuana users after a month of monitored abstinence.

Conclusions: Chronic marijuana use is associated with increasedcerebrovascular resistance through changes mediated, in part,in blood vessels or in the brain parenchyma. These findingsmight provide a partial explanation for the cognitive deficitsobserved in a similar group of marijuana users.

Source:  NEUROLOGY 2005;64:488-493