I found this post on Emerging Women today. It's about chronic physical illness, but the commentary in this post is relevant to mental issues as well.
Here's a snippet:
When I was a kid my mom struggled with the spiritual ramifications of her using her asthma medication; for a time she believed that doing so would prove her lack of faith in God, that if she managed to acquire enough faith she would be healed. It never happened and she's Publishsince moved on from that belief. Years later, someone who shared similar beliefs told me that I'd be cured of a fairly serious (though not life-threatening) allergy I have if I had enough faith. I didn't believe him, but that conversation has aroused some questions that I still grapple with in my mind.[Emerging Women: Theology of Chronic Illness]