Your choice of title makes it factually incorrect.  It does not <i>improve</i> lung function except at <i>very</i> low levels, and even that only applies to exhalation volume for the first second.  In fact, more than 1 joint every few days caused a pronounced <i>decrease</i> in lung function.<p>Hence the conclusion: &quot;<i>Occasional and low cumulative marijuana use</i> was <i>not</i> associated with <i>adverse</i> effects on pulmonary function.<p>Nothing there indicates or implies improvement.