Humanistic therapy is based on humanistic psychology, which has disadvantages that include a lack of concrete knowledge regarding specific treatments, an inability to help patients who are suffering from more severe problems and a reliance on generalizations, according to AllPsych. Many choose to use humanistic therapy as a foundation for change in patients, though some find that humanistic therapy is not sufficient as a stand-alone treatment.
Humanistic psychology is based heavily on the idea of a patient's free will. Because of this, humanistic therapy is usually ineffective at developing specific treatment techniques for the specific problems of a patient. It is also very difficult to evaluate the effectiveness of humanistic therapy with the same rigor with which other therapeutic techniques can be evaluated.
Humanistic therapy works best when used in dealing with minor problems regarding a patient's pathology or personality. It offers a severe disadvantage when used in treating something as serious and pervasive as schizophrenia.
An important disadvantage of humanistic therapy is that it relies on many generalizations regarding human behavior. It assumes that everybody is capable of performing moral actions and that all people are willing to act according to Maslow's hierarchy of needs. Humanistic therapy does not account for individuals acting against their own best interests. This puts the therapy at a disadvantage compared to other therapeutic techniques.