title: The impact of somatic symptoms on the course of major depressive disorder.
abstract: Somatic symptoms have been suggested to negatively affect the course of major depressive disorder (MDD). Mechanisms behind this association, however, remain elusive. This study examines the impact of somatic symptoms on MDD prognosis and aims to determine whether this effect can be explained by psychiatric characteristics, somatic diseases, lifestyle factors, and disability.
  
  
  
  In 463 MDD patients (mean age=44.9 years, 69.8% female) from the Netherlands Study of Depression and Anxiety (NESDA), we examined whether the type and number of somatic symptom clusters predicted the two-year persistence of MDD. Diagnoses of MDD were established with the Composite International Diagnostic Interview (CIDI) and somatic symptom clusters were assessed with the Four-Dimensional Symptom Questionnaire (4DSQ) somatization scale. Psychiatric characteristics, somatic diseases, lifestyle factors, and disability were taken into account as factors potentially underlying the association.
  
  
  
  The cardiopulmonary, gastrointestinal, and general cluster significantly predicted the two-year persistence of MDD, but only when two or more of these clusters were present (OR=2.32, 95% CI=1.51-3.57, p=<0.001). Although the association was partly explained by MDD severity, the presence of multiple somatic symptom clusters remained a significant predictor after considering all potentially underlying factors (OR=1.69, 95%CI=1.07-2.68, p=0.03).
  
  
  
  Somatic symptoms are predictors of a worse prognosis of MDD independent of psychiatric characteristics, somatic diseases, lifestyle factors, and disability. These results stress the importance of considering somatic symptoms in the diagnostic and treatment trajectory of patients with MDD. Future research should focus on identifying treatment modalities targeting depressive as well as somatic symptoms.
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation (ICPE), Groningen, The Netherlands. Electronic address: e.bekhuis@umcg.nl.
authors.forename: Ella
authors.initials: E
authors.lastname: Bekhuis
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation (ICPE), Groningen, The Netherlands.
authors.forename: Lynn
authors.initials: L
authors.lastname: Boschloo
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation (ICPE), Groningen, The Netherlands.
authors.forename: Judith G M
authors.initials: JG
authors.lastname: Rosmalen
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation (ICPE), Groningen, The Netherlands.
authors.forename: Marrit K
authors.initials: MK
authors.lastname: de Boer
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation (ICPE), Groningen, The Netherlands.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Schoevers
mesh_terms: D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000523:psychology; D016000:Cluster Analysis; D003865:Major Depressive Disorder / Q000523:psychology*; D005260:Female; D005767:Gastrointestinal Diseases / Q000523:psychology; D006801:Humans; D008019:Life Style; D016015:Logistic Models; D008297:Male; D000071896:Medically Unexplained Symptoms; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000523:psychology; D009426:Netherlands; D011379:Prognosis; D013001:Somatoform Disorders / Q000523:psychology*; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Course; Depressive disorder; Disability; Psychiatric characteristics; Somatic characteristics; Somatic symptoms