The association of comorbid anxiety disorders with suicide attempts and suicidal ideation in outpatients with bipolar disorder

Abstract

Individuals with bipolar disorder are at increased risk for suicide attempts and completion. Although anxiety may be a modifiable suicide risk factor among bipolar patients, anxiety disorder comorbidity has not been highlighted as critical in identification of high-risk individuals nor has its treatment been integrated into suicide prevention strategies. In this study, ancillary to the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD), 120 outpatients with bipolar disorder completed detailed assessment of suicidal ideation and behaviors. We examined the association of current and lifetime comorbid anxiety disorders with suicidal ideation and behaviors univariately and with adjustment for potential confounders in regression models. Lifetime anxiety disorders were associated with a more than doubling of the odds of a past suicide attempt, and current anxiety comorbidity was associated with a more than doubling of the odds of current suicidal ideation. Individuals with current anxiety disorders had more severe suicidal ideation, a greater belief suicide would provide relief, and a higher expectancy of future suicidal behaviors. However, some of these associations appeared to be better accounted for by measures of bipolar severity including an earlier age at bipolar onset and a lack of current bipolar recovery. Comorbid anxiety disorders may play a role in characteristics of bipolar disorder that then elevate risk for suicidal ideation and attempts. While further research is needed to establish the precise nature of these associations, our data support that the presence of comorbid anxiety disorders in individuals with bipolar disorder should trigger careful clinical assessment of suicide risk.

Introduction

Bipolar disorder has been clearly associated with elevated risk of suicidal ideation and attempts, with death due to suicide estimated to occur in 10–15% of patients (Angst et al., 2005, Goodwin and Jamison, 1990, Harris and Barraclough, 1997). The study of completed suicides and non-fatal suicide attempts in this high-risk group is important for establishing risk factors and potential strategies for suicide prevention. For completed suicides, common predictors include a history of suicide attempts, severity of depression, and hopelessness in patients with bipolar disorder (Hawton et al., 2005, Marangell et al., in press). By comparison, research on suicide attempts (SAs) and suicidal ideation (SI) has identified a broader range of predictors. In a recent meta-analysis of 23 studies, the main risk factors (defined as factors studied in more then one study and with a significant combined odds ratio greater than one) for non-fatal SAs included family suicide history, early age of onset, extent of depression, worsening affective episodes, mixed states, rapid cycling, and Axis I comorbidity, including specifically anxiety disorder comorbidity (Hawton et al., 2005).

Although anxiety disorder comorbidity may be critical for identifying high-risk bipolar patients, many important, well-designed studies of SI and SA in bipolar disorder have not examined the relationship of anxiety comorbidity with SA and SI (e.g., Fagiolini et al., 2004, Lopez et al., 2001, Oquendo et al., 2004, Oquendo et al., 2000). Among the studies that have examined this relationship, the role of comorbid anxiety disorders in escalating the risk of SI and SAs remains debated. While some studies have found an association of anxiety symptom or disorder comorbidity with history of SAs or SI in bipolar disorder (Engstrom et al., 2004, Fawcett et al., 1990, Simon et al., 2004b), other studies have failed to support this association under conditions of multivariate adjustment (Leverich et al., 2003, Slama et al., 2004), and others have even suggested that anxiety symptoms may be protective against SA (Slama et al., 2004). These studies vary in methodology, with variable use of validated assessments of SI, examination of proximal and longitudinal risk factors, and a combination of inpatient and outpatient samples. Furthermore, different combinations of potential risk factors have been statistically controlled (covaried) in these analyses, decreasing comparability of findings of anxiety as an “independent” risk factor.

Perhaps because of this debate in the literature, anxiety disorder comorbidity has not been highlighted as critical in the identification of high-risk bipolar individuals nor has its treatment been integrated into suicide prevention strategies, although anxiety may be a modifiable suicide risk factor (Fawcett et al., 1990). We sought to examine the association of anxiety disorder comorbidity by carefully assessing suicidal ideation and behaviors in a well-characterized sample of outpatients with bipolar disorder. We were interested in anxiety disorders as univariate predictors, representing their presence alone as a potential clinical marker of risk, as well as the effect of bipolar severity on this association.

We hypothesized that lifetime anxiety comorbidity would be associated with past suicide attempts, and that current anxiety comorbidity would be associated with greater current SI. We hypothesized that these associations would be reduced but still significant after adjustment for factors associated with bipolar disorder severity including earlier age at onset (Perlis et al., 2004) and the presence of significant current mood symptoms (i.e. lack of relative euthymia). Prior literature has also linked panic with bipolar severity (Feske et al., 2000, Frank et al., 2002, Simon et al., 2004b), panic attacks, panic disorder and social anxiety disorder (generalized type: GSAD) with SAs (Fawcett et al., 1990, Hall and Platt, 1999, Statham et al., 1998), and poorer bipolar course with GSAD (Otto et al., 2006). Accordingly, we hypothesized that panic disorder and GSAD would each be associated with SI and SAs independently of other comorbid anxiety disorders.