Diagnostic overlap of generalized anxiety disorder and major depressive disorder in a primary care sample

Generalized anxiety disorder (GAD) and major depressive disorder (MDD) are highly comorbid. A possible explanation is that they share four symptoms according to the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition-Text Revision (DSM-IV-TR). The present study addressed the symptom overlap of people meeting DSM-IV-TR diagnostic criteria for GAD, MDD, or both to investigate whether comorbidity might be explained by overlapping diagnostic criteria.

Participants (N = 1,218) were enrolled in the Coordinated Anxiety Learning and Management study (a randomized effectiveness clinical trial in primary care). Hypotheses were (1) the comorbid GAD/MDD group endorses the overlapping symptoms more than the nonoverlapping symptoms, and (2) the comorbid GAD/MDD group endorses the overlapping symptoms more than GAD only or MDD only groups, whereas differences would not occur for nonoverlapping symptoms.

The overlapping GAD/MDD symptoms were endorsed more by the comorbid group than the MDD group but not the GAD group when covarying for total symptom endorsement. Similarly, the comorbid group endorsed the overlapping symptoms more than the nonoverlapping symptoms and did not endorse the nonoverlapping symptoms more than the GAD or MDD groups when covarying for total symptom endorsement.

The results suggest that comorbidity of GAD and MDD is strongly influenced by diagnostic overlap. Results are discussed in terms of errors of diagnostic criteria, as well as models of shared psychopathology that account for diagnostic criteria overlap.