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Comorbidity was very common. Among 1,783 people with a current depressive and/or anxiety disorder, 67% of those with a depressive disorder had a current comorbid anxiety disorder and 75% had a lifetime anxiety disorder. Among those with a current anxiety disorder, 63% had a current comorbid depressive disorder and 81% had a lifetime depressive disorder.

Across the whole cohort, 40% had only 1 disorder, 30% had 2 depressive or anxiety disorders, and another 30% had 3 or more depressive or anxiety disorders.

The study found that comorbidity varied by diagnosis. In depressive disorders, social phobia and panic disorder were the most common current comorbid anxiety disorders, each occurring in about 41% to 42% of cases, and generalized anxiety disorder was also frequently present.

Compared with major depressive disorder, dysthymia had higher comorbidity rates, especially with social phobia and generalized anxiety disorder. Among anxiety disorders, depressive comorbidity was highest in generalized anxiety disorder and lowest in agoraphobia alone; for example, 76% of patients with generalized anxiety disorder had current major depressive disorder and 86% had lifetime major depressive disorder.

Comorbid anxiety and depressive disorders were independently associated with a higher-burden clinical profile. In the final multivariable model, comorbidity was associated with more childhood trauma (OR = 1.19; 95% CI, 1.06-1.33), higher neuroticism (OR = 1.05; 95% CI, 1.02-1.08), earlier age at onset of the first disorder (OR = 1.59; 95% CI, 1.22-2.07), longer duration of depressive and/or anxiety symptoms (OR = 1.01; 95% CI, 1.01-1.01), and higher symptom severity (ORs ranging from 1.01 to 1.03; all P values < .05).

Lower education was associated with comorbidity in an earlier model, but that association did not remain after clinical characteristics were included.

Yes. In patients with current comorbid depressive and anxiety disorders, anxiety preceded depression in 57% of cases, simultaneous onset occurred in 25%, and depression preceded anxiety in 18%.

The sequence varied by anxiety subtype. Social phobia preceded depressive disorders in 67% of cases, agoraphobia in 47%, and panic disorder in 39%, whereas generalized anxiety disorder most often had simultaneous onset with the depressive disorder at 41%.

Yes, but the differences were limited. Compared with comorbidity in which anxiety came first, comorbidity with preceding depression was associated with a shorter duration of depressive and/or anxiety symptoms (OR = 0.99; 95% CI, 0.98-0.99), later age at onset of the first disorder, reflected by lower odds of early onset (OR = 0.46; 95% CI, 0.31-0.68), and fewer fear symptoms (OR = 0.98; 95% CI, 0.97-0.99).

The study did not find associations of temporal sequence with sociodemographic variables or vulnerability factors such as childhood trauma.

The main clinical implication is that clinicians should routinely assess for both anxiety disorders and depressive disorders regardless of the primary reason for consultation. The authors reached this conclusion because comorbidity rates were very high and comorbid patients had more childhood trauma, higher neuroticism, earlier onset, longer symptom duration, and greater symptom severity than patients with pure disorders.

This was a cross-sectional analysis of baseline data from the Netherlands Study of Depression and Anxiety (NESDA). The analysis included 1,783 adults aged 18 to 65 years who had a current 12-month depressive disorder and/or anxiety disorder, with baseline data collected between September 2004 and February 2007.

Diagnoses were established with the Composite International Diagnostic Interview according to DSM-IV-TR criteria. Depressive disorders included major depressive disorder and dysthymia, and anxiety disorders included social phobia, panic disorder with or without agoraphobia, agoraphobia, and generalized anxiety disorder. Obsessive-compulsive disorder and posttraumatic stress disorder were not assessed in this study.

The main limitations were that the study was cross-sectional and relied partly on retrospective age-at-onset data. Because of the cross-sectional design, the findings do not allow causal inferences, and retrospective reporting of onset is subject to recall bias.

The study also assessed only selected common anxiety disorders, so obsessive-compulsive disorder and posttraumatic stress disorder were not included in the comorbidity analyses.