Marijuana reverse tolerance effect

Tolerance to the effects of marijuana clearly exist even though chronic users have described a reversed tolerance and claim that smaller doses of the drug are necessary to produce the desired effects. This effect is probably related to the manner of use and the expectations of the user. Chronic, high-dose cannabis users may experience an abstinence or withdrawal syndrome on abrupt discontinuation of use. Signs and symptoms include irritability, restlessness, nervousness, weight loss, insomnia, and rapid eye movement (REM) rebound. Onset of this syndrome is several hours after the last dose, and it lasts 4 to 5 d. Because withdrawal is not life-threatening, treatment involves little more than supportive therapy with short-term, low doses of benzodiazepines. 

Marijuana has several effects on the cardiovascular system, and can increase resting heart rate and supine blood pressure and cause postural hypotension. It is associated with an increase in myocardial oxygen demand and a decrease in oxygen supply. Peripheral vasodilatation, with increased blood flow, orthostatic hypotension, and tachycardia, can occur with normal recreational doses of cannabis. High doses of THC taken intravenously have often been associated with ventricular extra beats, a shortened PR interval, and reduced T wave amplitude, to which tolerance readily develops and which are reversible on withdrawal. While the other cardiovascular effects tend to decrease in chronic smokers, the degree of tachycardia continues to be exaggerated with exercise, as shown by bicycle ergometry. 

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