In essence, How and why are some therapists better than others? Understanding therapist effects, a book edited by Louis G. Castonguay and Clara E. Hill, is a review of how little scholars and practitioners know about the contribution made by therapists to the effectiveness of psychological interventions. The term therapist effects has been specifically coined to label the impact of clinicians’ individual characteristics, competencies, and actions on client outcomes, which can be statistically separated from the impact of type of treatment and clients’ symptomatology (encompassing needs and severity). Although therapist effects have been often ignored and treated as error variance in studies on the effectiveness of treatment interventions (outcome research), and their estimated size is rather small (i.e., approximately between 5% and 8% of the variance), they are currently being treated as a relevant, but still obscure entity in investigations of clinical trials, general practice, and specialty clinics.

Of course, the critical question to be asked concerns the ingredients that make some therapists more effective than others. Yet, before answering this question, it is necessary to clarify the criteria by which the outcomes of psychotherapy can be measured. Can change be estimated objectively by taking into account the assessment of therapists and the self-assessment of clients before, during, and after psychotherapy? Does the opinion of familiar others, such as family members, friends, and coworkers, need to be included so as to noticeably increase the validity and reliability of clinicians’ estimates of clients’ behavioral,  cognitive,  and emotional change? If clients’ views were the only measuring instruments, biases in the evaluation of the effectiveness of the treatment received may stem from clients’ need to justify their decision to undergo treatment, as well as their investment of money and time. Furthermore, clients, who generally enter psychotherapy during a crisis, may get better as the crisis subdues and the passage of time puts things in perspective. If therapists’ were the only measuring instruments, the evaluation of the effectiveness of the psychological treatment administered may be biased by self-justifications as well as by the justifications that clients use to enter therapy or interrupt it (which emphasize negative emotions), leave it (which emphasize well-being and positive emotions), and stay in touch if they are satisfied. Furthermore, comparisons of the individual characteristics, competencies, and behaviors of therapists are challenging. For instance, dropout rates may not only have a variety of sources, but also be defined differently. Records of the effects of psychotherapy in outcome research may be shaped by the conceptual models adopted. They also may be plagued by the size of the samples of therapists used as well as by the limited or incomplete records obtained.  Thus, it is not surprising that the portion of outcome research explicitly devoted to therapist effects has brought to the surface more questions than answers.

How can effectiveness be objectively (i.e., fairly) measured? Is there a well-articulated, consensus-based operational definition of therapists’ competence that encompasses the diversity of clients’ needs and therapists’ conceptual models? If competence is a matter of identifiable skills, what are the skills that therapists can acquire from training? Alternatively, is it a matter of being able to follow the protocol linked to a specific type of treatment that is the critical skill of effective therapists? The colorful assortment of conceptual models of therapies that exist on the market of psychological treatments, each emphasizing different aspects of human existence, leads to substantial differences in the way the needs of clients are conceptualized, addressed, and even measured during treatment. Can outliers, such as exceptionally successful and exceptionally mediocre clinicians, help scholars identify the cluster of factors that likely propel therapist effects across clients’ needs as well as the properties that may modulate such effects? If so, the issue of how to define success concretely, comprehensively, and consensually emerges as a sore thumb. Undeniably, outcome research focused on therapist effects remains a commendable but challenging enterprise that has yet to harvest mature fruits.

As the reader approaches the end of this well-written book, a series of themes start to take shape. First and foremost, evidence from a variety of investigations seems to point to a set of factors that may define the effectiveness of individuals who have been trained to offer psychological treatment. Rather than specific demographic characteristics, effective therapists seem to possess a cluster of abilities, such as handling negative reactions, superior processing of information, communicating empathy, respect and genuineness, embodying cultural competence and self-analysis, and establishing an effective working relationship with their clients. All abilities are said to be in the service of one key goal of treatment, namely, fostering the process of change. This array of abilities and the umbrella under which they serve are not surprising. In fact, it is not difficult to envision each suggested ability as having been generated by a layperson’s common sense, which, propelled by an elementary understanding of psychological treatment, is guided by his/her use of critical thinking skills. In this context, formalized data collection and complex statistical analysis seem more reassuring afterthoughts than the pillars upon which the identification of factors relies. It is not easy, however, to understand how each factor can be concretely represented in the day-to-day operations of therapists subscribing to different conceptual models and treating clients whose psychological distress varies in severity. Furthermore, statistical assessment of the magnitude of the contribution of each factor remains challenging in the complex environment of clinical work where several factors can independently or interactively contribute to client outcomes. Second, it is undeniable that the variability due to the therapist accounts for a small portion of the treatment outcome variance. Nevertheless, therapist effects play a role in the effectiveness of the treatment administered either alone or by interacting with the treatment administered and the needs of the client who received it. The extent of their contribution may be magnified or reduced as measurement instruments of data collection and statistical analysis are improved and new ones are developed. Third, if the amount of desirable change fostered in clients is the selected measure of effectiveness, most therapists cannot be classified as either unequivocally effective or ineffective. The existence of this amorphous group along with the fact that therapist effects increase in magnitude with the severity of the client’s symptomatology suggest that the ideal ingredients for therapeutic success (even if simply measured as magnitude of fostered change relative to target) may not only differ across clients’ needs, but also be hidden in the heterogeneity of the available data.   

The themes discussed above bring about unanswered questions which tickle the reader’s curiosity. Althougheach chapter of How and why are some therapists better than others? Understanding therapist effects, leads the reader to think of more questions than answers, it is an enlightening and engaging read. The reason is that it offers not only a panoramic view of a largely neglected field for which interest is now growing, but also an honest record of its struggles to produce findings that are valid,  reliable,  and helpful to practitioners. As a field of clinical psychological science, the literature on therapist effects offers scholars and practitioners alike opportunities to examine clinical work through the unbiased lenses of the scientific method, thereby not only increasing their understanding of psychotherapy, but also making clients’ investment in psychotherapeutic treatments smarter. Opportunities are palpable since fruits of outcome research have shed light on the relative effectiveness of different types of treatment in reference to clients’ needs and symptoms, and on the necessity to examine clinical work through the tools of the scientific method.

© 2017 Maura Pilotti

Maura Pilotti, PhD