INVITED COMMENTARIES Inflammation and Depression: Unraveling the Complex Interplay in Inflammatory Bowel Disease

D espite strong evidence implicating inflammation as a causal factor in some forms of depression, there are a number of issues to be resolved before this evidence can be translated into novel interventions. One such issue is the need to understand heterogeneity among individuals with inflammatory disorders and depression. In their report, Szigethy et al (1) described their attempt to tackle this issue using a sample of 226 adolescents with inflammatory bowel disease (IBD) and either minor or major depression. Specifically, the authors used latent profile analysis to identify 3 subgroups within their sample. Adolescents in profile 1 (75%) had mild depressive symptoms and relatively low levels of the systemic inflammatory markers C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Adolescents in profile 2 (19%) displayed high levels of anhedonia, fatigue, appetite change, physical complaints, irritability, depressed feelings, and psychomotor retardation as well as elevated CRP, ESR, and IBD activity. In contrast, adolescents in profile 3 (6%) had high levels of morbid ideation, suicidal ideation, weeping, hopelessness, anxiety, fatigue, and depressed feelings, but levels of CRP and ESR that were similar to those seen in profile 1. The most pronounced differences between adolescents in profiles 2 and 3 were in depressed affect and motor hypoactivity (highest in profile 2) and hopelessness and suicidal ideation (highest in profile 3). There are a number of reasons to welcome this addition to the literature on inflammation and depression. First, the study focused on adolescents with IBD, a group that has received relatively less attention in the field of psychoneuroimmunology to date. Second, the study also focused on subgroups within the population of patients with depression, an important topic because not all individuals with depression have elevated inflammation and not all individuals with elevated inflammation have high levels of depression. Finally, the article yields information that may prove infor-