Can anybody name this mysterious biological 'effect'?

there is this mysterious effect i always try to recall but cant remember nothing can anybody name it i just recall the savo word so here is the description of the effect: there was a test going on somewhere some sick patients were given false medicines but were not told that they were false they just believed that the medicine was real and after few days all miraculously recovered by only the power of believing i don't know the level of their sickness i herd it on discovery Chanel 6-7 years ago can anybody has even heard about it if yes please tell me about this weird effect and please sorry for my poor description