Not every answer is in scripture. You wouldn't consult the Bible when you need to change the spark plugs in your call, and you probably wouldn't call the local Baptist church when your hard drive crashes.
The Bible is not a technical manual. But it will provide the freedom of thought and expression for the Watts and Newtons of this world. Would you go to Autozone to fix your depression? I do believe the Bible does have the answers to life and conquering such things as depression. You are wrong on that.
So do you believe that depression is never due to organic causes? Do you believe the same about Alzheimer's? If not, on what basis do you make a distinction between the two?