Objectives: In an attempt to reduce the phenotypical heterogeneity in an ongoing genetic study of suicidal behavior, we investigated the impact of comorbid anxiety disorders on suicidal behavior in bipolar disorder (BD) patients.
Methods: Anxiety disorders were compared in 406 BD I and BD II patients with or without lifetime history of suicide attempt.
Results: Among anxiety disorders, only social phobia (SP) was significantly associated with history of suicide attempt in BD [p < 0.001, odds ratio 4.26 (2.284–7.946)]. Moreover, onset of SP was found to precede onset of BD.
Conclusions: This result suggests that SP is an important risk factor for suicidal behavior in BD. Further studies are required to determine whether comorbid SP may help to identify a more homogeneous BD sub-group, especially when studies of suicidal behavior are conducted. A second question is whether SP identifies a sub-group of subjects with BD who have a more severe illness course and whether treatment of SP with selective serotonin reuptake inhibitor (SSRI) antidepressants is associated with improvement or worsening of the course of BD.