Marihuana and human physical activity.

Adult male volunteers with a prior history of either moderate (N = 12) or heavy (N = 14) marihuana use were systematically observed before, during and after a 21-day period of free access to 1 g 2% delta-9 THC marihuana cigarettes. A matched sample of casual alcohol drinkers (N = 11) served as a control group. Sleep and other molar behaviors were observed hourly to obtain a representative sample of daily activity. Both moderate and heavy users were less active immediately after marihuana use and slept more on days following heavier consumption. Heavy users reduced their waking activity on days following heavier consumption, as well as during the entire period of marihuana availability. These reactions did not persist beyond the period of availability for either group. The findings suggest a dose-related delayed reaction to heavy marihuana consumption which disappears following the cessation of regular use. However, changes in activity following single doses of marihuana may be related more to the social circumstances of its use than to its pharmacological action.