The substantial differences among states, age groups, races, and genders in recent surveys of the prevalence of depression and other mental illnesses in adults illustrate the importance of expanding the mental health focus of surveillance and information systems to help guide national and state-level planning, according to a report released Sept. 1 by the Centers for Disease Control and Prevention.
The report describes the results of population-based surveys from selected CDC surveillance systems administered at different points during 2004-2009. The surveys indicate that southeastern states, non-Hispanic blacks, and women have the highest prevalence of depression, postpartum depression, serious psychological distress, and mentally unhealthy days per month.
However, these estimates of the prevalence of mental illness are limited by the generality of the surveys. None of the surveys, which include the state-based Behavioral Risk Factor Surveillance System (BRFSS), the Pregnancy Risk Assessment Monitoring System (PRAMS), the National Health and Nutrition Examination Survey (NHANES), and the National Health Interview Survey (NHIS), was designed solely to monitor mental illness. They have instead "added components on mental illness gradually over time as recognition of the importance of mental illness in public health has increased," wrote Dr. William C. Reeves of the CDC’s Public Health Surveillance Program Office and his colleagues (MMWR 2011;60[Suppl.]:1-29).
For instance, the BRFSS – a telephone survey of 450,000 adults in 50 states, the District of Columbia, and some territories – found a rate of depression of 8.7% in 2006 in respondents from 38 states, the District of Columbia, and territories, compared with 8.2% in 2008 in 16 states.
The number of states that conduct the BRFSS with one or two small, optional mental illness modules varies from year to year. In 2006 and 2008, depression occurred most often in Mississippi and West Virginia (13.7%) and least often in North Dakota (4.3%). Women had higher prevalences during these years (about 10%), compared with men (about 7%). Non-Hispanic blacks also had a higher prevalence of depression (11%-13%) than did non-Hispanic whites (about 8%) or Hispanics (about 10%).
Not all states collect data from the optional modules "because of financial constraints, competing state surveillance priorities, and limitations in the length of time respondents are willing to spend completing a telephone survey," the authors wrote.
National results with NHANES data indicate a prevalence of depression of 6.8% during 2005-2008, with rates of 8.4% in women, 4.9% in men, 9.7% in non-Hispanic blacks, 6.2% in non-Hispanic whites, and 7.2% among Mexican Americans.
The 22 states that conducted the PRAMS during 2004-2008 found that symptoms of postpartum depression affected 14.5% of respondents. This rate varied from a low of 10.3% among women aged 30-39 years to 23.3% among women aged 19 years or younger, and a low of 9.8% in Minnesota to a high of 21.3% in Tennessee. Non-Hispanic black women had a higher prevalence (21.5%) than did Hispanic (16.8%) and non-Hispanic white women (11.9%).
The prevalence of serious psychological distress, as defined by scores on the Kessler-6 Psychological Distress Scale, was 3.2% in 2009 in the NHIS. The same scale in the BRFSS revealed that serious psychological distress occurred in 4% in 35 states in 2007 and in 3.9% in 16 states in 2009. During those periods, the rate varied from 1.9% in Utah to 9.4% in Tennessee. The Kessler-6 definition of serious psychological distress is associated with anxiety disorders and depression but does not identify a specific mental illness.
All states and territories report the mean number of "mentally unhealthy days" per month in the BRFSS because it is a core feature of the survey. In 2009, the mean number was 3.5 days and was highest overall in the southeastern states. The mean number of days also was higher among non-Hispanic blacks (4.1) and women (4.0).
On the BRFSS, lifetime diagnoses of depression occurred in about 16% of respondents in both 2006 and 2008 despite differing numbers of participating states. Lifetime diagnoses of anxiety disorders were reported by 11.3% in 2006 and by 12.3% in 2008. The authors pointed out a general lack of data on anxiety disorders in CDC surveys and noted that "better documentation of the impact of anxiety disorders might help guide national public health policy. At the state and local levels, documenting the prevalence and impact of anxiety disorders might help ascertain the need for additional public health services for these disorders."
Lifetime diagnoses for other disorders were reported in the NHIS in 2007: 1.7 % of respondents reported a diagnosis of bipolar disorder and 0.6% reported schizophrenia.
Dr. Reeves and his associates also wrote that surveys of health care providers, such as the National Ambulatory Medical Care Survey (NAMCS), the National Hospital Ambulatory Medical Care Survey (NHAMCS), the National Hospital Discharge Survey (NHDS), and the National Nursing Home Survey (NNHS), "complement data from the population-based surveys to provide a more complete representation of the occurrence of mental illness in the United States."