Dear One-Hit Wonder,

Smoking marijuana can have a variety of effects on your mind and body, but pupil dilation is not one of them. In fact, studies have shown that smoking marijuana may actually cause the pupils to constrict, rather than dilate. However, the decrease in pupil size may be so slight that a very precise measuring tool would have to be used to observe the effect.

There may be a couple possible explanations for this mistake about marijuana. Some people speculate that the commonly held belief that smoking pot causes the pupils to dilate originated from the belief that people usually smoke marijuana in dimly lit places. Pupils naturally dilate more in dimly lit environments in order to allow more light to reach the retina and improve a person's ability to see. This occurs whether or not a person smokes marijuana. Other people may just confuse marijuana's effects and the effects of other drugs that cause the pupils to dilate (e.g., cocaine and LSD).

Alice

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