"Christian psychology" as the term is used today is an oxymoron. The word "psychology" no longer speaks of studying the souls instead it describes a diverse menagerie of therapies and theories that are fundamentally humanistic. The presuppositions and most of the doctrine of psychology cannot be successfully integrated with Christian truth. Moreover, the infusion of psychology into the teaching of the church has blurred the line between behavior modification and sanctification...If one is a truly Christian psychologist, he must be doing soul work in the realm of the deep things of the Word and spirit- not fooling around in the shallows of behavior modification... There may be no more serious threat to the life of the church today than the stampede to embrace the doctrines of secular psychology. They are a mass of human ideas that Satan has placed in the church as if they were powerful, life-changing truths from God. Most psychologists epitomize neo-Gnosticism, claiming to have secret knowledge for solving people's real problems. There are even those psychologists who claim to perform a therapeutic technique they call "Christian counseling" but in reality are using secular theory to treat spiritual problems with biblical references tacked on. ~John MacArthur
If all we had was God's Word, that would be enough.