How many of these myths have you heard of?

1. One joint equals a pack of cigarettes.

This hoary old favorite comes back again and again, seemingly impervious to the onslaught of the real world.

Prohibitionists earnestly tell us that smoking just one joint “equals a pack of cigarettes.” Or maybe it’s 16, or maybe just four cigarettes; they seem a little unclear on the exact number.

This fallacious conclusion is derived from a study by Dr. Donald Tashkin in which the UCLA researcher examined airflow resistance in the lungs of tobacco smokers compared to that in the lungs of marijuana smokers. Dr. Tashkin did find that daily pot smokers experience a “mild but significant” increase in airflow resistance in the large airways, greater than that seen in persons smoking 16 cigarettes per day.

But what they don’t tell you is that, ironically, Dr. Tashkin also found – in the largest study ever of its kind – other, more important markers of lung health, in which marijuana smokers did much better than tobacco smokers. In the four years since Dr. Tashkin’s latest study results were announced, I’ve never heard a single anti-marijuana speaker mention this.

They also never seem to have time to mention that Dr. Tashkin’s study unexpectedly found that smoking marijuana – even regularly and heavily! – does not lead to lung cancer.

Dr. Tashkin said these results “were against our expectations.”

“We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use,” Dr. Tashkin said. “What we found instead was no assication at all, and even a suggestion of some protective effect.” Continue reading