Reefer Madness (1936)
From the opening crawl:
The Motion Picture you are about to witness may startle you. It would not have been possible, otherwise, to sufficiently emphasize the frightful toll of the new drug menace which is destroying the youth of America in alarmingly increasing numbers.
Marihuana is that drug. A violent narcotic — an unspeakable scourge — The Real Public Enemy Number One!
Its first effect is sudden, violent, uncontrollable laughter; then come dangerous hallucinations — space expands — time slows down, almost stands still… fixed ideas come next, conjuring up monstrous extravagances, the total inability to direct thoughts, the loss of all power to resist physical emotions… leading finally to acts of shocking violence… ending in often incurable insanity.
In picturing its soul-destroying effects, no attempt was made to equivocate. The scenes and incidents, which are fictionalized, are based upon actual research into the results of Marihuana addiction.
If their stark reality will make you think, will make you aware that something must be done to wipe out this ghastly menace, then this picture will not have failed in its purpose. Because the dread Marihuana may be reaching forth for your son or daughter… or yours…OR YOURS!”
“Violent narcotic”…? Allright, whatever you say, Mr. Movie Man.
Watch the entire thing for free here!