There are as many theories of Christian Counseling as there are people who consider themselves to be Christian counselors, but here are some controversial points from one counselor's point of view.
All counseling is spiritual, in a broad sense, because all human issues have meaning. And questions of meaning always lead to further questions of meaning. As humans, we cannot stop asking the questions until we get to one, final Answer To All the Questions (ATAQ!). Does ATAQ even exist? If it does, it must be God; and even if it doesn't exist, you, as a human, cannot help wanting there to be ATAQ.
But Christian Counseling has a difference: it starts with the assumption that both client and counselor are Christians. Both of us believe (on our good days) that the Answer To All Questions really exists and that the route to this ATAQ is through the Christian faith.
There is research that shows that various spiritual practices help people to function better. If you pray regularly, you are less likely to be depressed, and you are less likely to be anxious. This stands to reason, from the Christian Counseling point of view. If God made us to worship Him, then we will be happiest worshiping Him.
But there are two distinctions that need to be made.
First, top-down counseling is not always the most effective way to get to your goal. What does that mean?
Suppose you came to counseling because you could not lose weight as well as you wanted. We find out together that a major problem for you is driving past the doughnut shop on the way to work and coming home. Now we can talk about reasons for wanting to be in good health--you want to honor your spouse, you want to live a long and healthy life and enjoy your grandkids, you want to look good for your class reunion, you believe that your body is the "temple of the Lord" and so you want to honor God.
Now, actually, all of these reasons can be tracked back to your longing for God: everyone wants relationship, to love and be loved, and the perfect love is only found in God. Everyone wants to be the most excellent version of themselves and to be appreciated (ultimate perfection and appreciation found only in God).
But notice that your longing for God is expressed in many varied ways, not just meditation on the things of the Lord (although that is definitely necessary and good!). So the way to help you love God better is also not necessarily directly spiritual--it can also be practical. In this case, along with thinking deeply about whether you are looking for God in the wrong places, it might also be very helpful to drive a different route to work. I have found that practical solutions often help people find short-term success...which then leads to much more energy and joy in their walk with God. If only they were easier to put into practice!
Second, Christian Counseling means that we are really eager to help people feel better, decrease or get rid of symptoms, and so forth, just like any counselor. But it mainly means that we have an end-goal in mind that is a little different from usual counseling goals.
If you work hard, as a client, and get rid of every single symptom found in the Diagnostic and Statistical Manual of the American Psychiatric Association (the notorious DSM-5), that is good. But it does not mean that you are happy, because being truly happy means fully flourishing as a human being. It would not be worth it to take a different route home, lose 25 pounds, and get big-headed about it! From our shared Christian perspective, being happy means learning to know and love God better and better.
So, Christian Counseling: Get it? Got it? Good!