Psychiatric Epidemiology, 3rd edition covers the epidemiological literature of anxiety disorders based on DSM III, DSM III R, DSM IV or ICD-9 criteria. It begins by referencing The NCS-R study, which estimated the lifetime prevalence of any anxiety disorder at 28.8%. The ESEMed study on the other hand, reported a life time prevalence of 13.6% using data from European nations, 17.5% in women and 9.5% in men. The Who WHM Survey collected face to face survey data from 17 countries, finding a lifetime risk in the US of 47.4%, significantly different to that of Nigeria at 12%. Overall, anxiety disorders were found to be the most prevalent psychiatric disorders in ten countries.
Other interesting findings to mention include higher prevalence rates of GAD, PD, and social anxiety disorder in whites in the 2001-2003 NSAL study. Despite higher prevalence rates, African Americans and black Caribbeans who did not meet criteria for anxiety disorders reported greater levels of impairment. The NLAAS nationally sampled Latino and Asian respondents, finding a lifetime prevalence rate estimate of any CIDI/ DSM IV anxiety disorder of 15.7%, compared to 25.7% found in NCS-R data on non-Latino subjects. Consistent with past literature, it also found a lower lifetime prevalence of GAD, PTSD, PD and Social Phobia, with Puerto Ricans having the highest lifetime prevalence of any psychiatric disorder compared to other Latinos. For anxiety disorders, the immigrant paradox was only observed in Mexican subjects. This signaled a large variety within the US Latino population based on differences in ethnicity and birthplace.
Surveys using DSM III showed consistency in the six month prevalence of panic disorder, ranging from .6/100 in CT to 1.1/100 in Puerto Rico. Using DSM III R, the NCD found a lifetime rate of 3.5/100. The NCS-R on the other hand found a lifetime rate of panic disorder of 4.7/100 based on DSM IV criteria. All studies found higher rates of panic disorder for women than for men.
Based on NCS and ECA data, there was a bimodal distribution of age of onset (15-24 year range and 45-54 year range in both men and women). The lowest lifetime prevalence rates were found in persons 65 and over. On the contrary, Puerto Rican and Hispanic women’s lifetime prevalence increased with age in the ECA data. This differed with men, whose lifetime rate dropped with each age group. The NCS found no ethnic differences in younger adults, but lower rates in non-whites in comparison to white older age groups.
The NCS-R found a lower risk for non-Hispanic blacks compared to Hispanics and non-Hispanics whites. A cross national study in ten different countries found that the lifetime prevalence rates for DIS/DSM III panic disorder ranged from 1.4/100 to 2.9/100. It demonstrated a high consistency of panic disorder’s prevalence across cultures, a higher prevalence rate in women, and that panic disorder is strongly associated with an increased risk of major depression and agoraphobia across all counties in the study.
The chapter also reports findings on comorbid psychiatric disorders. The NCS for instance, reported that a majority of those with anxiety disorder had comorbid major depression. 12 month and lifetime comorbidity was also strongly linked to impairment and attempts of suicide when compared to non-comorbid disorders. A 2001-2002 NESARC random sample survey reported that 20% of people with a current substance use disorder experienced a mood or anxiety disorder within that past year.
Based on the ECA study high consistency was reported in 6 month prevalence rates of agoraphobia, although there was a high variation in lifetime rates (1.1 in urban Taiwan vs. 6.9 in Puerto Rico). ECA and NCS studies showed high consistencies in terms of lifetime prevalence, 5.6 and 5.3, respectively. Similarly to panic disorder, lifetime prevalence rates for agoraphobia were higher in women. The ECA and NCS studies reported lifetime prevalence rates for agoraphobia to be highest among African Americans. Both the NCS and NSAL found agoraphobia to be inversely related to education and poverty level. The chapter touches base on the relationship between panic attacks, panic disorder and agoraphobia, stating that Agoraphobia can only be coded as panic disorder with agoraphobia or agoraphobia without history of panic disorder on the DSM IV TR.
Lifetime rates of social phobia differed from a low of .4 in rural Taiwan to a high of 3.9 in New Zealand, possibly due to cultural differences or translation methods. Lifetime DSM III R social phobia was significantly higher than other DSM III studies, speculatively as a result of broader DSM III R criteria. DSM IV criteria yielded lower estimates of lifetime social phobia.
Lifetime rates of social phobia were highest in women, persons between the ages of 18 and 29, and in those who were less educated, single, and in lower socioeconomic statuses The NCS reported similar findings. Analysis of NCS-R and NLAAS data found a higher lifetime prevalence of social phobia among NCS-R white subjects than NLAAS Latino subjects, 14.3% and 7.5%, respectively. For NCS-R whites, lifetime prevalence was higher for US born subjects than immigrants, 16.9% and 8.8% respectively. For NLAAS Latino subjects, higher lifetime prevalence of social phobia was found only in US born Mexican subjects at 10%, compared to Mexican immigrants at 4.7%. No difference was found in other Latino ethnicities.
The ECA study reported a one year prevalence of 2.7/100 for generalized anxiety disorder. Lifetime prevalence was consistent. Despite distinct diagnostic criteria, ECA and NCS rates for generalized anxiety disorder were very similar. Combined data from three ECA study sites found one year prevalence of GAD to be higher in females, African Americans, and persons under 30 years of age. Based on the NSAL, 12 month prevalence of GAD was significantly higher for whites than African American and Caribbean Blacks. Significant higher lifetime prevalence of GAD was found among whites compared to Latino subjects, 8.6% and 4.1% respectively. The 2001-2002 NESARC study found a 12 month prevalence of GAD for men to be 1.2% and 2.7% for women. Lifetime prevalence rates for men and women were 2.8% and 5.3%, respectively. Men with GAD were found to have a higher risk for comorbid substance use compared to women.
Six month prevalence of OCD using DSM-III, DSM-III-R or DSM-IV criteria varied from .7/100 in Los Angeles to 2.1/100 in Piedmont, NC. Lifetime prevalence ranged from .3/100 in Taiwan to 3.2/100 in Puerto Rico. Studies in English language sites demonstrated a general consensus. These rates contradicted past literature portraying OCD as a rare disorder.
Like other anxiety disorders, prevalence rates of OCD were higher among women than men in the ECA study. After gender comparisons were controlled for factors like marital status, employment status, ethnicity and age, there were no differences between the genders.
After the occurrence of natural and mass disasters, The NSAL reported a 12 month prevalence rate of 3.7% for PTSD. Higher rates were found in women, younger cohorts, and those below the poverty line. Lifetime risk of PTSD was 8.4% for Caribbean blacks, 9.1% for African Americans and 6.8% among Whites. The ESEMed found a 12-month prevalence of 1.1%, with higher rates for women.
An example of an occurring disaster is the September 11 terrorist attacks. A study using the PTSD Checklist found a DSM II R PTSD diagnosis rate of 11.2% in NYC, 2.7% in Washington, 3.6% in other metro areas, and 4% among residents in non-metro areas. Major depression prevalence after 6 months of attack in a sample of NYC residents was 9.4%. Evidence suggests that exposure to a mass traumatic event is a strong environmental risk for the development of these disorders. Timing of post-disaster assessment and the long term effects of massive disasters are essential topic of focus for future investigations.
The chapter further discloses limitations in the epidemiologic studies referenced. The NCS-R study for instance, underrepresented homeless, institutionalized, and non-English speaking populations in their sample. In addition, participant reports were likely conservative on the fear of reporting embarrassing behaviors. The chapter closes addressing future developments in research. These include but are not limited to studying the long term impacts of natural and mass disasters on the occurrence of PTSD and anxiety disorders, explaining higher rates of PD, GAD, and Social Phobia in women, the immigrant paradox found in Mexicans but no other subgroups in the Latino population, comorbidity between psychiatric disorders, and prevalence rate variations found within factors like race and ethnicity. All of these factors may provide clues of causation that help improve our understanding of biological and psychological interactions’ impact on anxiety disorders.
