Over at The Straight Dope, a reader writes:

Various health and yoga websites claim that iceberg lettuce contains chemicals similar to laudanum, morphine, or other opiates. There are also reports of people being admitted to hospitals after injecting themselves with lettuce extracts, and papers about smoking lettuce. I have found no information about the chemical constitution of lettuce that mentions morphine or opiates. Are there such things in supermarket lettuce? –Curious Lettuce Eater, via e-mail

Cecil replies:

You’re thinking: How can iceberg lettuce be a drug? It barely qualifies as a food. Little do you know. While the stuff from the supermarket isn’t likely to do much, lettuce generally speaking does contain psychoactive compounds. Enough to get you high? Hard to say. Judging from available evidence, the stuff might do nothing, give you a buzz, or kill you. Here’s what we know:

Read the rest at The Straight Dope