Margit Kooijman

Therapist effects | 109 Discussion The present study suggests that a therapist effect exists in the rehabilitation of patients with shoulder complaints in primary care physiotherapy settings. The physiotherapist explained 12% of variance in change of severity of the shoulder complaint, which on average decreased by 5.0 points. Additionally, the personality trait extraversion showed a significant association (p = 0.03) with change in treatment outcome, indicating that therapists who tend to be more outgoing and energetic achieve better treatment results. The size of the therapist effect found in current study is in accordance with existing literature from the psychotherapy profession and higher than figures found within the field of physiotherapy 3-5 . Since most of these studies were RCTs restricting freedom of variability in treatment options and thereby variety between therapists, a higher therapist effect could indeed have been expected in observational research 16 . One study did allow choice of treatment by therapists but found no effect 4 . However, due to small sample size and thus small variation between therapists, treatment turned out to be limited mainly to manual therapy. Hence this lack of therapist effect was not surprising as Lewis et al. (2010) showed that therapist effect is smaller in this type of therapy than in behavioural treatment strategies 3 . The result with respect to the influence of personality traits is more difficult to put into perspective. As far as we know, only one study investigated these traits in physiotherapy settings so far; it showed that patients with chronic diseases treated by less neurotic physiotherapists achieved better outcome compared to patients treated by therapists who were less calm, secure and resilient 5 . Univariate analysis in current study also indicated a possible association of neuroticism with outcome. However, in the final model, only extraversion was found to significantly influence severity of complaints. Extraversion includes traits as sociability, assertiveness and positive emotionality. On the introvert-extravert spectrum, we recognise those who get energized by being around other people as more extraverted personalities and those who get energized by being with themselves as introverts. This could be one explanation as to why this trait is positively associated with decrease of complaints; possibly patients sense this way of making contact and get energized themselves to engage actively in their treatment process. Two studies within the field of psychotherapy specifically investigated the effect of the BIG 5 personality traits on outcome 17,18 . Their findings suggest influence of several personality traits on satisfaction of the patient and on the patient-therapist working alliance. Yet, associations were moderated by duration of the physician-patient relationship, age, medical burden of the patient, the levels of each trait and it was even suggested that the relationship might be non-linear by nature. In summary, there is scant research on this topic and results are known to interact with many other factors whilst the influence of patient characteristics has, as