Trajectories of somatic drug utilization patterns in Major Depressive Disorder: A Study protocol for a Danish nationwide register study using Latent Class Analysis

Abstract

Background: Major Depressive disorder (MDD) is a heterogeneous, multi-etiological disorder that is associated with chronic medical conditions and a high somatic treatment burden. A better understanding of the somatic diseases and treatment burden in MDD can be provided through a mapping of the somatic drug utilization patterns over time. The objective of this study is therefore to characterize the somatic drug profiles and their transitions over time (i.e. trajectories) among MDD patients. Methods: This descriptive study will be a nationwide register-based study including all Danish patients with an incident MDD diagnosis between 2011 and 2015. Using Latent Class Analysis, we will identify homogenous MDD patient subgroups according to somatic drug utilization (i.e. drug profiles). The development in somatic drug profiles will be depicted in four different time intervals from three years prior to the MDD diagnosis to three years after the diagnosis. Patients will be assigned to the latent class (drug profile) to which they have the highest probability of belonging using modal assignment. The treatment trajectories will be performed by cross tabulating these assignments. Discussion: Profiles and trajectories of somatic drug use will provide a new perspective on patterns of somatic drug burden in MDD patients. Moreover, identifying homogenous subgroups of MDD patients regarding somatic drug use can contribute to a deeper understanding of MDD etiology. In the future, this knowledge could help optimizing MDD treatment by studying if different antidepressants will show different efficacy and safety depending on the profiles and trajectories of somatic diseases.