In psychological research in the 70s (I think - I can't find the exact sources), subliminal messages were flashed to mental patients, neurotics and control groups, mostly in order to test several of Sigmund Freud's theories. Actually, they were probably trying to disprove the theories, but failed.
The experiment went like this: the patients and control groups were flashed subliminal messages that according to Freud, were supposed to accentuate their behaviour. For example, Freud claimed that schizophrenia was associated with oral fixation and that stuttering was associated with anal fixation. If this is correct, then subliminal messages related to the oral stage should elicit a change in the schizophrenic behaviour in schizophrenics, while it should affect the stutterers much less. Likewise, anal-related messages should affect stutterers and not schizophrenics.
Experimentees were flashed two different subliminal messags, both unnerving, but one generally unnerving, and one associated with the psychological stage. So, schizophrenics were flashed "A man kills another man" and "A cannibal eats another man", or something of the sort. Stutterers were flashed with things on the line of "I need to eat" and "I need to shit".
The results were surprising: Stutterers exhibited more stuttering after being flashed with anal messages, than normal messages. Stutterers flashed with oral messages did not exhibit accentuated stuttering, (i.e. there was no difference between stutterers flashed with "A man kills..." and "A cannibal eats..."). Schizophrenics reacted to oral messages, i.e. schizophrenics flashed with oral-related messages exhibited more schizophrenic behaviour (their behaviour was appraised by nurses).
This strongly supports Freud's theories, unlikely as they seem. An interesting note: when flashed with "Mommy loves me", an improvement was detected in everyone.