Comorbid Mental Disorders in Anxiety Disorders: Genetic Aspects of Bipolar Disorders and of Ethnicity

Abstract

Anxiety disorder (AD) is commonly comorbid with other mental illness. It could be a state or trait, controversially. Evidence for an association between alcoholism and anxiety has emerged from clinical studies of patients with alcoholism, and those of patients with anxiety disorders. Alcohol dependence (or abuse) as well as bipolar disorder (BP) is usually comorbid with anxiety disorder and/or depressive disorder, which often coexist and are difficult to distinguish from one another. However, in Han Chinese population, the comorbidity rate either with alcoholism or bipolar disorder was not reported as much high as reported in Caucasians, this finding of comorbidity between anxiety/depressive disorders and alcohol dependence (or abuse) or/and bipolar disorders, possibly at the genetic level, makes the differentiation of their categorical diagnoses in the association study vitally important. AbbreviationsAD: anxiety disorder ALDH2: aldehyde dehydrogenase 2 ANX/DEP ALC: anxiety/depression alcoholism BDNF: brain-derived neurotrophic factor BP: bipolar disorder DOPAC: 3,4-dihydroxyphenylacetic acid DOPAL: 3,4-dihydroxyphenylacetaldehyde DRD2: dopamine D2 receptor DRD3: dopamine D3 receptor GAD: generalized anxiety disorder PTSD: post-traumatic stress disorder PD: panic disorder OCD: obsession compulsive disorder MAOA: monoamine oxidase A

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

“…Ethnic differences have also been noted in epidemiological studies[74]. Notably, some reviews have found lower rates of anxiety disorders among Asian patients with BD; genetic differences have been proposed to account for this finding[69,122,135].…”

“…Conversely, only a few studies have been unable to find this relationship between anxiety disorders and SUDs in BD[9,28,113]. The presence of a combination of anxiety disorders and SUDs in BD not only complicates the diagnosis, but also impairs treatment response and can lead to a more severe course of illness and increased suicidal risk[10,17,27,69,154]. Apart from associated SUD comorbidity, anxiety disorders in BD have also been linked with other comorbid conditions such as attention deficit hyperkinetic disorders, eating disorders, and a range of personality disorders[9,14,18,22,42].…”

“…This inconsistent association between anxiety disorders and bipolar subtypes has also been found in other reviews[8,10,15-17], in epidemiological studies[78,81,82,84,91], and in clinical samples of patients with BD[52,100,120]. On the other hand, more than a few reviews have reported a considerably higher prevalence of bipolar spectrum disorders[7,42,46,66,128], sub-threshold BD, or subsyndromal bipolar symptoms[7,14,66,69,139] among comorbid anxiety and BDs.…”

“…The first possibility is supported by studies indicating that anxiety disorders serve as prodromal conditions preceding the development of BD[7,11,45,175,176]. The second possibility of BD contributing to emergence of anxiety disorders is indicated by the evidence suggesting that anxiety symptoms are an integral part of BD[6,8,16], by the episodic course of anxiety disorders in a subset of patients with BD and anxiety disorders[177], by familial genetic links between the two disorders[9,10,17,69,178], and by the benefits of mood stabilization as a primary mode of treatment[3,6,9,10]. The third model posits that higher-order pathophysiological mechanisms contribute to the onset of both anxiety disorders and BD.…”

“…The list of such core pathophysiological processes includes familial genetic, neurobiological, and psychosocial factors. There is reasonable evidence suggesting genetic links between anxiety disorders and BD[69,130,157], particularly for panic disorder[53,57,112,128,179] and OCD[40,42,70,176,178]. Neurotransmitter disturbances, structural and functional brain changes, and alterations of synaptic plasticity could also provide the common link[9,10,20,53,130].…”