Comorbidity of bipolar and anxiety disorders: An overview of trends in research

Table 5 Correlates and impact of anxiety disorder comorbidity in bipolar disorder

	Principal findings	Ref.
Demographic correlates
Age	Higher prevalence in younger patients with BD	[8,20,30,32,40,42]
	No differences in rates according to age	[9,33,36,70]
Gender	Higher prevalence among women	[8-10,14,16-18,24, 40]
	No gender differences	[30,32,33,36,42,52,69,70]
Marital status	No differences according to marital status	[20,70]
Education	Higher levels more comorbidity	[20]
	Lower levels greater comorbidity	[8,9,14,66]
	No effect of education	[33,36,70]
Socioeconomic status	Greater comorbidity among those with lower socioeconomic status	[8,9,14,74]
	No effect of socioeconomic status	[33,36]
Ethnic and cross-national differences	Differences in comorbidity across nations and ethnicities	[11,16,19,30,69,74,135]
Clinical correlates
Age of onset	Lower age of onset is associated with higher levels of comorbidity	[8-10,14,16-18,20,21-24,27,30,31,33,36,40,42,49,52,56,57,60,66,70,136-142]
BP I vs BP II	Greater comorbidity in BP I	[15,17,30,33,49,60,84]
	Greater comorbidity in BP II	[4,9,20,128]
	No clear differences in comorbidity between BP I and BP II	[7,8,10,16,18,19,28,32,36,42,50,52,66,69,78-81,93,137]
Depression	Anxiety comorbidity is associated with more frequent and severe depressive episodes	[8,10,14-17,26,36,42,49,52,57,66,69,137-139,143]
	No clear evidence of predominance of depressive pathology	[19,28,70]
Mania	Anxiety comorbidity is associated with more frequent and severe manic episodes	[8,16,19]
	No clear evidence of association with mania	[14,18,28,36,40,49,70]
Euthymia	Anxiety comorbidity is associated with shorter durations of euthymia	[8,9,14,16,17,21,22,50,52,66,67,69]
Rapid cycling and mixed features	Anxiety comorbidity is associated with rapid cycling and mixed states	[8-10,13,15-18,40,49,52,67,69,141,142]
	No association with rapid cycling and mixed features	[19,28,66,70,144]
Psychotic symptoms	Anxiety comorbidity is associated with psychotic symptoms	[5,8,16,20,22,25,40]
	No association with psychotic symptoms	[70]
Insight	Anxiety comorbidity is associated with greater insight	[9]
Cognitive impairment	Anxiety comorbidity is associated with greater cognitive impairment	[15, 66]
Bipolar spectrum	Anxiety comorbidity is associated with bipolar spectrum disorders	[7,8,40,42,45,46,66,128]
Subsyndromal symptoms	Anxiety comorbidity is associated with subsyndromal symptoms	[14,66,69,139]
Substance-use disorders	Anxiety comorbidity is associated with greater prevalence of substance use and substance use disorders	[5,8-10,12-14,16-18,20,22-25,27,40,42,50,57,60,66,67,69,70,139,141-143]
Other comorbidity	Anxiety comorbidity is associated with greater prevalence of ADHD, eating disorders, personality disorders.	[9,12,14,20,22,42,139,145]
Impact
Course of illness	Anxiety comorbidity is associated with poorer course and outcome in BD in terms of greater illness severity, frequent episodes, and greater risk of hospitalization	[5,8-10,13-18,20,22,23,26,27,33,36,40,42,49,52,56,57,60,70,128,137-139,141-143,146]
Treatment response	Anxiety comorbidity is associated with poorer treatment response in BD	[4-6,8-10,12-14,16-18,22-27,40,49,57,60,66,67,69,137-139,141,142,146,147]
Suicide	Anxiety comorbidity is associated with increased risk of suicidality in BD	[4,5,8-10,13,14-18,21-27,33,36,40,42,49,50,52,57,60,66,67,69,128, 136-139,141,142,148,149]
Functioning	Anxiety comorbidity is associated with impaired functioning in BD	[8-10,14-18,21,22,25,27,33,36,40,42,49,50,66,67,69,128,139]
Quality of life	Anxiety comorbidity is associated with impaired quality of life in BD	[8-10,14-17,21,22,25,27,36,39,42,50,66,67,138,139]
Outcome of BD	Anxiety comorbidity is associated with incomplete remission and recovery in BD	[5,8,10,14,16,17,21,22,26,36,50,66,69,128,138]
Adherence	Anxiety comorbidity is associated with irregular treatment-adherence in BD	[10,16]
Delayed diagnosis-costs-service utilization	Anxiety comorbidity is associated with delayed diagnosis increased health-care utilization and costs in BD	[24,27,41,49 69,137]

BD: Bipolar disorder; BP I: Bipolar disorder subtype I; BP II: Bipolar disorder subtype II; ADHD: Attention deficit hyperactivity disorder.