Generalized anxiety disorder and psychiatric comorbidities such as depression, bipolar disorder, and substance abuse.

Generalized anxiety disorder (GAD) has a high rate of comorbidity with other psychiatric disorders, including major depressive disorder (MDD), bipolar disorder, other anxiety disorders, and substance use disorders. The similarities between GAD and MDD have led some to suggest that GAD should be reclassified as a mood disorder. The concurrence of GAD with another disorder heightens a patient's risk for impairment, disability, and suicidality. Clinical trials for GAD and disorders that are most likely to occur with GAD have generally not taken comorbidity into account, and there is a paucity of data guiding how comorbidity should inform treatment selection. Research into the biology and psychopathology underlying the high rate of comorbidity of GAD and into efficacious interventions for GAD with comorbidity is needed.