I don't mean you can cure a depression easily this way. But you can switch it off temporarily and let the patient experience a totally different perspective for at least some moments. In many cases this may help a lot. Many people believe what they see is always what exists and what they feel is always what the situation is. Knowing (as a result of your own experience!) you can have drastically different feelings about the same reality depending on chemicals you ingest change a lot: you know your fear, anger or apathy don't represent the objective reality (nor your self) and you don't have to act the way they push you any more.