Is wild lettuce the same as opium?

The short answer

The nickname "lettuce opium" refers to lactucarium, wild lettuce's dried milky latex, which physically resembles opium and was historically used as a milder substitute for it. Its actual active compounds, lactucin and lactucopicrin, act weakly on GABA-A receptors — the same broad receptor family as benzodiazepines and alcohol — not on opioid receptors at all. The resemblance is in appearance and historical use, not pharmacology.