The relationship between clinical complexity, treatment dose and outcome in everyday clinical practice

Background and objectives: Observational studies reveal only small correlations between patient characteristics and outcome. Thus, the clinical impression that some patients are harder to treat than others is not reflected in different treatment outcomes. Possibly, in observational research the prognostic value of patient characteristics is masked by the amount of treatment received by the patient. According to this idea, patients with complex problems receive more treatment and will achieve the same outcome at the end of treatment as less complex patients. The treatment dose may mediate the relationship between clinical complexity and outcome. Method: This hypothesis was investigated in a national database with treatment outcomes of patients in curative care for mild to moderately severe psychiatric problems, predominantly mood and anxiety disorders. Complexity of the patients was operationalized based on the severity of care demands; treatment dose was measured by amount of treatment and length of the treatment period; treatment outcome was assessed with self-report questionnaires for symptomatology. Results: On average, treatments with more complex patients involve more minutes of treatment, last longer, and lead to a less favourable outcome compared to less complex patients. Although statistically significant, these associations were not strong. The variance within the patient groups remained large and the prognostic value of complexity for treatment dose and for outcome of treatment was small. Conclusions: The relationship between complexity and outcome was not clearly mediated by treatment dose. Other variables, such as unmeasured patient characteristics, the nature of the treatment, characteristics of the therapist, the therapeutic relationship or the culture of the institution may be more important predictors of the treatment outcome and deserve further study. (C) 2019 Asociacion Universitaria de Zaragoza para el Progreso de la Psiquiatria y la Salud Mental. Published by Elsevier Espana, S.L.U. All rights reserved.