I have taken many perspectives on the question of mental health over the years. I’ve experienced a lot of stuff in my family.
I myself have Asperger’s, and I have struggled with depression over the years.
First, I have found that the most effective way to deal with depression is to do the Spiritual Exercises of St. Ignatius. That and listen to Fr. Corapi.
But one thing we have to start with when it comes to “mental illness” is “how much of this is really disordered? And how much is it that my approach to my God-given abilities is disordered?”
In a biological sense, I think most “mental illnesses” have advantages. As someone pointed out, many saints–indeed, all saints–would be diagnosed by modern clinicians as “mentally ill.”
In some ways, we were better at dealing with these things in the Middle Ages. Back then, they knew there were "good crazies’ and “bad crazies”: some people were mentally “ill” yet had deep spiritual insights, moral fervor, etc. Others, however, were harmful to themselves and others, malicious, etc.
Someone said that, if it weren’t for people with autism and asperger’s, we’d be living in caves. Autism and Asperger’s have their difficult aspects, mostly invovling social interaction, but they also give people great mathematical and creative abilities.
Schizophrenics tend to have keen spiritual and psychological insights: if you really pay attention to what a schizophrenic is saying, there’s a certain “code,” but a lot of it is deeper truth than most people are willing to acknowledge. My schizophrenic brother-in-law would write on his blog about me "attacking him in his dreams’ on nights that (unbeknownst to him) I was fasting and praying for him.
Bipolar makes people more emotionally committed.
A hyperactive person, once focused on a task, will accomplish a lot more than others could.
I could go on.
Some people talk these days about neurodiversity: understanidng how God made different brain types for different purposes.
That said, when we have these differences, we still develop problems because we are not properly guided and, more importantly, society abuses us for our differences.
That’s where therapy, medication, etc., come in.
And if you need medical therapy, get it, and use it.
Taking Prozac, or Ritalin, or anti-psychotics for a malfunctinoing brain is no different than taking Tenormin or Coumadin for a malfunctioning heart.
If you can get a miraculous cure through prayer, great. But if you don’t, that doesn’t mean God doesn’t care. It means that God trusts you enough to let you suffer without the miracle: “Blessed is (s)he who has not seen yet still believes.”