Objectives: Major depressive disorder (MDD) is one of the most disabling mental illnesses and it has a significant impact on society. This review aims to provide updated scientific evidence about the epidemiology of MDD. Methods: A systematic literature review of the PubMed and MEDLINE databases was performed to identify articles on the prevalence of MDD and its correlates. The search was restricted to manuscripts published between January 2001 and December 2018. Results: Sixty-three articles were included in the review. The lifetime prevalence of MDD ranged from 2 to 21%, with the highest rates found in some European countries and the lowest in some Asian countries. The main sociodemographic correlates were separated/divorced marital status and female gender. Child abuse, intimate partner violence, and comorbidity with other physical and mental disorders also were consistently associated with MDD across the reviewed studies. Conclusions: MDD is a highly prevalent condition worldwide. There are remarkable interregional differences in the disorder’s prevalence, as well as in certain sociodemographic correlates. MDD is also highly comorbid with physical and mental health problems.

The working alliance is one of the most widely studied constructs in psychotherapy process research. The purpose of our study was to adapt the patient and therapist forms of the Working Alliance Inventory (WAI-P and WAI-T) into Spanish. Both measurement instruments were translated into Spanish through a systematic translation process. The psychometric properties of the instruments were evaluated in both a pilot study and a clinical study involving Spanish outpatients with depressive disorders and their therapists. In the clinical study, patients completed the Spanish-language Beck Depression Inventory (BDI) prior to initiating therapy and after the third and tenth psychotherapy sessions. High average scores were obtained with the Spanish-language WAI-P and WAI-T. A large number of individual items correlated satisfactorily with the overall score for the corresponding subscale. Both measures demonstrated excellent reliability (internal consistency) and convergent validity. There were some limitations in the discriminant validity of the measures vs. measures of empathy. Regarding predictive validity, the overall WAI-P and the Task subscale of the WAI-T separately explained a moderate percentage of the variance in patient change in the BDI after the tenth psychotherapy session. These results were satisfactory and consistent with those obtained in studies using the English-language WAI.

La alianza de trabajo es uno de los constructos mas estudiados en investigacion de procesos en psicoterapia. El objetivo de nuestra investigacion fue adaptar las versiones del paciente y del terapeuta del Working Alliance Inventory (WAI-P y WAI-T) a la lengua espahola. Ambos instrumentos de medida fueron traducidos al espahol mediante un proceso reglado de traduccion. Sus propiedades psicometricas fueron examinadas en un estudio piloto y en un estudio clinico en el que participaron pacientes ambulatorios con trastornos depresivos y sus correspondientes terapeutas. En el estudio clinico, los pacientes completaron la adaptacion espahola del Beck Depression Inventory (BDI) antes del tratarmento y despues de la tercera y de la decima sesion de psicoterapia. El WAI-P y el WAI-T en espahol exhibieron altas puntuaciones medias. Un elevado numero de sus items correlaciono de manera adecuada con la puntuacion total de su respectiva subescala. Ambas pruebas evidenciaron una excelente fiabilidad (consistencia interna) y una excelente validez convergente. Su validez discriminante exhibio algunas limitaciones cuando ambas medidas correlacionaron con dos pruebas de empatia. En cuanto a la validez predictiva, el WAI-P total y la subescala tareas del WAI-T explicaron por separado un porcentaje moderado de la varianza del cambio de los pacientes en el BDI despues de la decima sesion de psicoterapia. Estos resultados fueron satisfactorios y coherentes con los hallados en los estudios que han empleado las correspondientes versiones originales del WAI en ingles.