There are circumstances that can truly distort a person's thoughts and emotions. Reactive attachment disorder is one such: the child learns at a very early age that they cannot trust their caregiver to meet needs. This can cause difficulties for the child for the rest of his/her life--makes it difficult, or nearly impossible, to form healthy bonds with other people. This kind of thing isn't treated with drugs (or should not be), but with therapy, if the therapist is willing to put in the time and effort. I have an adopted aunt who has RAD who adopted a child from Russia who also has RAD. Being family to them takes effort and understanding, but they are both better for the help that they've received and are able to lead somewhat normal lives.
To answer a previous poster, there is a major difficulty with finding real physical evidence regarding the chemical imbalances in the brain that contribute to depression, bipolar d/t, schizophrenia and others--you can't slice into someone's living brain to watch the firing of the nerves, and once the brain is dead (autopsy time), the nerves are not producing their chemicals. I've personally seen psych meds make living possible for many people. Sometimes, it's a single depressive episode and the medication helps normalize the patient long enough for emotional healing to occur and the person moves on and never needs it again. Sometimes it's a long-term affair that again allows the person to lead a more balanced life. It can be over done, meds are often used instead of therapy because a lot of people want a quick fix rather than the hard work of learning to change their thought patterns and emotional responses, which is what a good therapist will teach a person to do.
It's easy to say "give up your anxiety to God. He'll fix it," without going through the long, sometimes emotionally messy process of helping them learn how to give it to God. There are things that take longer to "get over," such as a young girl being used as payment for her mother's meth, or a child being tied to a chair until he soiled himself and being force-fed the waste. "Don't worry; dwell on the positives not the negatives" is a useless platitude to the 10-year-old girl who's afraid she might be pregnant by her daddy who goes to her pastor for help and is raped by the pastor. Sometimes it takes more to help people with backgrounds like these to be healthy and sane than simply telling them to "read your Bible and pray more." They learn how to think and feel in a way that allows them to survive the abuse, and when they get out of the situation, their thought processes are broken beyond what a lot of people are willing to help with, or have any idea of where to even start. A good therapist will be able to help this person see how their coping mechanisms were situation specific and are destructive to a healthy life and can help them unravel their tangled thoughts and emotions. My dad is a therapist of this kind. He has lead many of his counselees to Christ through his counseling, as only Christ can fully heal a person's mind/emotions. God does use people for this though, as He uses doctors to perform surgeries, set broken bones or give chemo.