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Thanks to you, my depression really does just vanish.
Literal
Truly your thanks-to [means-で] my depression [topic-は] blows-away-[completion-てしまう].
Two notable features. おかげで ('thanks to,' literally 'with [someone's] shadow') is the standard grateful expression for a positive outcome; its negative counterpart is せいで ('because of [your fault]'), used to assign blame. The compound verb 消し飛ぶ ('erase-and-fly,' i.e. to be wiped clean away) paired with ~てしまう emphasizes that the depression is completely, almost surprisingly obliterated — ~てしまう here carries the completive nuance more than the regretful one.