Cannabis: persistent adverse effects on cerebral blood flow

Heavy smokers of cannabis show changes in blood flow in the cerebral arteries, even after a period of abstinence than a month, U.S. researchers report in the latest issue of "Neurology" magazine.

The deleterious impact of cannabis on cerebral blood flow may be responsible, at least in part, cognitive deficits already observed in some studies of heavy users of marijuana or after acute intoxication, assume Ronald Herning and colleagues from the National Institute on Drug Abuse in Baltimore.

The team of U.S. researchers has examined whether the effects of the use of this drug on cerebral blood flow persist after a period of abstinence and whether the deficits observed in the long term depends on the intensity of the initial consumption.

Their work focused on observations made with 54 cannabis smokers and 18 control individuals. The researchers observed the blood flow in the cerebral arteries of the participants by making them undergo transcranial Doppler ultrasound. After an initial examination for all participants at the beginning of the study, a second scan was performed in cannabis smokers, after a month of abstinence.

The blood flow velocity in brain arteries was greater among cannabis users than among the control, not only at the time of inclusion in the study, but after a month of abstinence.

U.S. researchers also found that among marijuana users, the pulsatility index reached the most important participants in the control group values. This indicator, which measures the resistance vessels to blood flow, blood reflects constriction could be an alteration of self capacity of the circulatory system.

"The marijuana users had slightly higher than those of people with chronic high blood pressure or diabetes pulsatility index values," said Ronald Herning in a statement released by the American Academy of Neurology. "However, these values showed lower than those obtained in demented patients. This suggests that marijuana use leads to abnormalities in the small blood vessels of the brain, because similar pulsatility indices were observed in other diseases affecting vessels blood, "he says.

After a month of abstinence, this indicator showed an improvement in small and medium cannabis (categories covering people smoking 2 to 15 joints per week and 17-70 weeks not attached), the authors note.

However, this withdrawal period had no effect on the values stored in heavy cannabis users (from 78 to 350 joints per week).

Regular and important cannabis use is associated with changes in cerebral blood flow a month of abstinence does not recover, the authors conclude. According to them, additional analyzes are needed to investigate the mechanisms linking a major marijuana and changes in the circulatory system.