Mental illness is an interesting consideration, because it creates incongruities with normal Christadelphian theology. In practice within the community there is a big difficulty with depression and many Christadelphians, (including well regarded speakers) are on various forms of medication.
This is at odds with their stated views of scripture. To put the Christadelphian position simply - there is one right way of thinking, which is found within the Bible and when understood correctly allows the mind of God to grow in us. We have the right thinking to the degree therefore that we have the knowledge of the Bible in us. Anything apart from that by contrast is the wrong thinking. The idea posited is that although we are all physical (with neither soul nor spirit), we are divided within that into a mind that has the power (with the Bible in us) to discipline the body. The “natural thinking” is called “the thinking of the flesh” and the “spiritual thinking” is called the “thinking of the spirit.”
Quite logically then to take psychological advice from psychologists is to take advice from those whose understanding is “that of the flesh.” If someone has the wrong thinking the solution would seem to be to get more of the Bible (or the right thinking) in them.
The truth therefore is that reading the Bible does not always provide the spiritual, mental or emotional help that is claimed and that at times is pragmatically acknowledged by Christadelphians not in their words, but in their actions.
In other areas of both secular and psychological thought, the “thinking of the world” is considered to be humanistic. This creates a situation where within the Christadelphian community they have and accept their Care Groups using the psychological approaches of “the world” but elsewhere such thinking is rejected.
The practical difficulty is an intellectual approach based upon the acquisition of Bible knowledge as the way to change doesn’t seem to be very effective in dealing with certain mental and emotional difficulties.