Strong depression and anxiety covariation in bipolar disorder
MedWire News: Researchers have found that anxiety is strongly and persistently associated with depressive symptoms in patients with bipolar disorder.
Erkki Isometsä, from the University of Helsinki in Finland, and colleagues note that this is important because understanding the covariation of disorders in patients with bipolar I or II disorder helps to improve the descriptive validity of the conditions.
“The descriptive validation of these disorders is crucial for the development of the DSM-V and to advance etiological research,” they say.
The researchers therefore analyzed data from the Jorvi Bipolar Study (JoBS), involving 191 patients with DSM-IV bipolar I or II disorder, to examine correlations between mood symptoms and Axis I disorder comorbidity.
The participants were evaluated with the Structured Interview for DSM-IV Disorders, with psychotic screen, plus symptoms scales at the start of the study and again at 6 and 18 months.
At intake, all patients had a current illness episode, and most were euthymic or had depressive symptoms or were in a major depressive phase at follow-up. About 60% of patients had a comorbid Axis I disorder at the start of the study and 32.6% had a comorbid Axis I disorder at all three evaluations.
By 18 months, 81.2% of patients had had a comorbid Axis I disorder during their lifetime, 57.6% had suffered anxiety, 54.9% had experienced substance use disorders, and 22.2% had had eating disorders.
There was a clear association between anxiety disorders and depression, with 43.6–56.5% of patients with a current major depressive phase found to have concurrent anxiety disorder. The proportion was only slightly lower in patients with depressive symptoms only.
Also, anxiety disorders were the most prevalent and stable of the comorbid disorders; one in four patients with an anxiety disorder at baseline exhibited the disorder in all three evaluations.
The strong, stable association between bipolar depression and anxiety was confirmed using structural equation modeling, and a latent change model (LCM) confirmed the association at the individual level.
The LCM findings indicated that patients with a high Beck Anxiety Inventory (BAI) score at baseline showed less improvement in Beck Depression Inventory (BDI) scores at follow-up, and that improvements in BDI scores were associated with a similar improvement in BAI scores.
With regard to other comorbidities, eating disorders were associated with depressive symptoms, and substance use disorders covaried with manic symptoms, but these comorbidities were more rare and transient than anxiety.
Isometsä and team conclude in the journal Bipolar Disorders that “none of the comorbid disorders followed a course independent of bipolar disorder, but comorbidities differed in how strongly they covaried with mood.”
They add that the covariation of depression and anxiety seen in their study may, “to a degree, be interpreted as manifestations of the same illness propensity.”
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By Lucy Piper