174 Chapter 5 These characteristics could be at the GP level, if physicians prone to prescribe less often antidepressants were able to self-select into local groups with higher supply of psychological support; or at the local group level, if those groups with more psychologists were also the local groups where mental health services are better integrated, and local protocols, training or clinical leadership favour the practices reducing the prescription of antidepressants. Our study adds to the body of literature exploring the relationship between pharmacological and non-pharmacological approaches to treat depression, which is mostly composed by GP surveys and qualitative studies susceptible to limitations as selfreporting, desirability bias or real-life contradictions between GPs intentions and nonpharmacological resources available to them [14]. We provide two main contributions to this field of research, which are relevant to several other countries that face similar challenges in access to non-pharmacological treatment approaches, such as financial barriers or long waiting lists [14]. First, we observed that the effect of supplying additional psychological therapy resources to GPs might depend on what the baseline level of these services is, especially in a context scarcity. Adding one psychologist/100,000 patients reduced GP prescription of antidepressants by 2.9% when none or just one psychologist worked at the local group (lowest quartile); and by 4.4% for GPs working in local groups with the highest supply of psychological resources (highest quartile). No effect was found in middle quartiles. These findings suggest that (some) GPs are willing to substitute the prescription of antidepressants by referrals to psychologists when faced with the opportunity of shifting care for the first time, but that additional supply might be used based on patients’ severity, possibly by prioritizing combined therapy for moderate patients and only using psychotherapy alone as a substitute again when higher severity patient needs would be covered by larger teams of psychologists. While our data does not allow us to investigate this hypothesis further, literature suggests that most GPs still prefer to use psychotherapy in a combined treatment approach, despite their positive opinions about psychotherapy effectiveness [14, 23, 34]. A second contribution is not directly related to the effects of increasing psychotherapy in prescription behavior, but to the confounders associated with both. Our between term suggested that GPs prescribing less are also those exposed to the higher average number of psychologists/100,000 patients, for reasons we cannot account for. Confounders could be at the GP-level and patient-level, for example unobservable beliefs and personal experiences of GPs if they self-select into local groups with larger number of psychologists or influence the decision of hiring psychologists in their local group (for example through their prescription patterns). However, both our institutional setting and robustness analyses8 exclude GP and patient-level confounders as the main 8 Table A2 shows that lagged antidepressant prescription behaviour is not associated with the changes in the number of psychologists.
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