Anxiety Disease Background

Introduction

Anxiety disorders are disorders that have common features of excessive fear and anxiety with related behavioral disturbances. They commonly coexist with depressive symptoms or major depressive disorder especially in patients with severe anxiety.

Epidemiology

Generalized Anxiety Disorder (GAD)  

The prevalence of generalized anxiety disorder is 0.9% among adolescents and 2.9% in adults in the general population of the United States (US). While the prevalence in other countries ranges from 0.4-3.6%. Notably, there is lower incidence of generalized anxiety disorder among Asians, Africans, native Americans, and Pacific Islanders compared to Europeans. The morbidity risk is noted to be 9% and usually occurs in middle-aged individuals. The ratio of occurrence in females to males is 2:1.  

Panic Disorder (PD)  

The prevalence of panic disorder is estimated to be at 2-3% in adults and adolescents in the general population across the US and several European countries. There are lower rates of panic disorder among Latinos, African Americans, Caribbean blacks, and Asian Americans. There are higher rates among American Indians and non-Latino whites. The prevalence of panic disorder is estimated to be 0.1-0.8% in Asia, Africa, and Latin American countries.  The ratio of occurrence in females to males is 2:1 with lower prevalence rates in children <14 years of age. Peak prevalence of panic disorder is during adulthood and then declines in individuals >64 years of age.  

Social Anxiety Disorder  

The prevalence rate of social anxiety disorder in the US is approximately 7% while in Europe it is 2.3%. There are comparable prevalence rates in children and adolescents with rates decreasing with age. The prevalence rates among adults range from 2-5%. The odds ratio of females to males ranges from 1.5-2.2.

Anxiety_Disease Background

Pathophysiology

The pathogenesis of anxiety disorders is not well understood. However, they may stem from a complex interplay of biological, psychological, and social or environmental factors. Firstly, genetic factors have been noted to predispose individuals to the development of GAD. Notably, twin studies have shown significant familial aggregation among GAD, panic disorder, phobias, and obsessive-compulsive disorder. The heritability of anxiety disorders varies from around 30-35% to as high as 50-60%. Secondly, patients with anxiety disorders show hyperactivation of the amygdala in response to anxiety cues. Studies have also shown perturbed coordination of brain circuitry between the amygdala and prefrontal cortex in patients suffering from GAD. Additionally, PET scans show significant increase in glucose metabolism in the amygdala, thalamus, medulla, right posterior temporal love, inferior gyrus, cerebellum, and right frontal gyrus in patients with GAD and PD. Lastly, it has been shown that individuals with anxiety disorders show bias toward threat-related stimuli, with distortions consistent with their anxiety. These biases include hypervigilance for possibly threatening stimuli, overinterpretation of neutral stimuli as threatening, and increased attention for potentially threatening stimuli. This threat bias in cognitive processing of information is consistently seen in anxiety disorders.