One of the guiding principles for healthcare in today’s National Healthcare System is high-quality care that is effective, safe and focused on patient experience (Choices NHS, 2013). For a treatment to be effective, it must be driven by theory and based on evidence. According to Hollin (1995), the definition of treatment integrity is “that the programme is conducted in practice as intended in theory and design”. Thus, a clear description of the components of each treatment is crucial; manuals tend to do that in a greater or lesser degree.Publicly funded healthcare systems, such as the NHS, demand time-limited but highly effective, empirically supported treatments for common mental health disorders. As NICE states at its national clinical guidelines for common mental disorders “evidence-based treatments are often delivered within the context of an overall treatment programme….it is important to maintain and enhance the service context in which these interventions are delivered otherwise the specific benefits of effective interventions will be lost” (National Institute for Health and Clinical Excellence, 2011). The profoundly structured nature of treatment manuals achieves exactly this, to deliver strikingly efficient and more highly focused therapy than might otherwise be the case (Fairburn et al., 1993). They are widely accepted and have been used to describe treatments and train therapists since the 1960s (Lambert & Ogles, 1988). The level of therapists’ adherence to treatment manuals is, however, a controversial topic. Theoretically speaking, high levels of therapist adherence to a manual should result in better treatment outcomes, as long as the treatment is delivered in practice as is intended in theory (Emmelkamp, Bouman & Blaauw, 1994; Schulte et al., 1992). Therefore, strictly following a manual can be beneficial for less experienced therapists, since it can provide them with the support and structure that is essential during the first years of their careers. In fact, less experienced therapists tend to have higher levels of adherence than more experienced ones (Henry et al., 1993; Siqueland et al., 2000). This is possibly because variability in treatment outcome amongst inexperienced therapists is found to be very wide (Crits-Christoph et al., 1991) and so, strict obedience to a manual can eliminate that, by offering them a minimum quality assurance.On the contrary, Crits-Christoph et al. (1991) discovered that variability amongst more experienced practitioners tends to be really small, and so, thoughtless compliance as opposed to clinical tact may result in losing the best that manualised treatments have to offer (Horvath & Luborsky, 1993, p. 580). Importantly, the therapist risks being left with nothing if the treatment doesn’t work with a specific patient (Persons, 1991, p. 101), since many manuals demonstrate therapy transcripts of ideal patients who eagerly accept interventions and appear to improve steadily over the course of treatment. This is not always the case in clinical practice, as some patients appear to be more resistant and reluctant to change induced by therapy, than others. Moreover, rigid compliance to a manual may have counter-therapeutic effects. Addis (1997) describes how a therapist who reacts to a hostile patient who struggles to communicate his thoughts “with repeated attempts to assess and challenge thought processes…could create a negative cycle resulting in drop out or increased resistance to change” (p. 5). High levels of adherence to specific technical procedures are also found to interfere with the development of a good therapeutic relationship (Henry, Strupp et al., 1993) and with positive outcomes (Castonguay et al., 1996). Consequently, the therapist who chooses to use a manual in a more flexible way, alongside the hypothesis-testing approach, can more easily react to treatment failure and adapt the treatment so that it can be effective with different types of patients.Moreover, therapy manuals are the result of outcome studies, which have been frequently criticised for being unrepresentative of clinical practice. Therefore, the standardised manual-based treatments they employ can’t make room for the heterogeneity within diagnostic categories, due to the screening for homogenous samples that takes place during such studies (Persons, 1998). Undoubtedly, therapists working at publicly-funded healthcare systems seem to come across more diverse and complex cases, since most clinical disorders are defined by heterogeneity, with different maintaining variables for each patient (Poland, Von Eckardt & Spaulding, 1994). Thus, rigid adherence to a manual leaves no room for individual case formulation that would reveal the particular factors involved in the development and maintenance of the patient’s problems, since, as Davison & Lazarus (1995) suggested, manuals lack at analysing single cases ideographically. That being said, patients face the risk of receiving a generic therapy, not tailored to their individual needs, cognitive, behavioural, emotional and physiological symptoms, while therapists turn into automatons, leaving aside their “consummate empathic understanding, sensitivity, tact and skill” required for therapy (Strupp & Anderson, 1997).On the other hand, the majority of treatment manuals include multiple components, increasing the probability of them being effective with various patients whose disorders are maintained by different variables. At some disorders, the core similarities amongst patients are much more important for their treatment, than any possible individual differences (Silverman, 1991). What is more, the core part of clinical case formulation requires from the therapist to process a vast quantity of complex information, which is prone to an element of cognitive bias. Therefore, strictly complying with a manual can be proven superior to individual case formulation, by eliminating the additional sources of error introduced by subjective judgemental process.Admittedly, many patients referred to a therapist within the NHS tend to present more than one disorder. According to psychiatric epidemiology, common mental disorders tend to cluster together (Kessler, McGonagle et al., 1994); therefore, rigid compliance to a manual that is designed for a particular disorder may seem ineffective in treating cases of co-morbidity. In addition, manuals can be more effective with patients presenting with clearly defined disorders, while more flexibility may be required when dealing with patients that present with less defined disorders.However, in such cases, clinicians must choose which problem to tackle first, as multiple disorders cannot be treated all at once. Indeed, in some situations, a primary target of change can be distinguished, while in others a sequential treatment is much more preferred. Moreover, several studies have proven that the elimination of one disorder can result in generalised improvement and clinically significant reductions in co-morbid disorders (Fairburn, Kirk, O’Connor & Cooper, 1986; Garner et al., 1993; Brown et al., 1995; Hickling & Blanchard, 2003). As a result, a clinician who is adhering strictly to a manual and providing the best possible therapy in the most effective way while working on one disorder could actually eliminate the rest of the disorders and lead to generalised improvements. Moreover, therapists who rigidly follow a treatment manual may face the undesired effect of governing their behaviour with specified rules, rather than focus on the ongoing interaction with a patient. This way, the clinician may adhere to the technical requirements, but not necessarily to the competence with which treatment should be implemented (Schaeffer, 1983; Binder, 1993; Waltz et al., 1993). Thus, most manuals advise on flexibility on the part of the therapist, or even warn against the use of manualised treatments in a rigid, stereotyped way (Beck, 1979). Clinical skills are necessary in order to develop communication, rapport, therapeutic alliance and trust, to elicit and address individual needs and concerns, to deal with hesitation about change, as well as to increase the likelihood of compliance. Therapists play a critical role in helping their patients overcome ambivalence about change and promoting commitment to it, despite possible psychological setbacks (Fairburn et al., 1993; Wilson, Fairburn & Agras, 1997). Manuals clearly cannot provide all the information required for the development of those skills and therefore, rigid compliance to those can only provide the therapist with a gross index of the therapy practices, but it cannot quite capture the essence of it. More importantly, there is the risk of obfuscating clinical artistry and some extremely important elements of the therapy (Davison & Lazarus, 1995), since psychological treatment is more than just the application of certain techniques described in a manual.To summarise, psychological treatment cannot be compared with the sterile, stepwise process of surgery, as it is a process intensely interpersonal, and, ultimately ideographic. As a consequence, the very specificity of techniques that enables treatment manuals to increase the quality of mental health care could result in ineffective rule-governed practice when therapists rigidly comply with them. Therapeutic skills in evidence-based treatments are apparently found halfway between totally rigid adherence at one end and sole reliance on clinical judgement at the other. The goal is clinical sophistication rather than “thoughtless compliance” (Luborski & Horvath 1993, p. 580). Considering the amount of variance associated with unidentified patient variables and unexplained variance, it is impossible to know a priori what factors will arise for a given therapist-patient pairing and so, manuals tend to fall flat from this perspective. In other words, for manuals to achieve their full utility therapists are required to do more than rigid rule-following; they must be able to breathe life into them.