A preliminary study says the psychedelic chemical in “magic mushrooms” may ease depression in some hard-to-treat patients. The effects in a study released Wednesday were modest but they occurred with a single dose in people who previously had gotten little relief from standard antidepressants. The study is part of a resurgence of research into potential medical uses of hallucinogenic drugs, and the results echo findings in smaller studies of the mushroom compound psilocybin. The compound was taken by capsule during medically supervised sessions lasting up to eight hours. The researchers say larger and longer studies are needed to determine the effectiveness and safety of using the chemical for depression.