The Stress in America™ survey was conducted online within the United States by Harris Interactive on behalf of the American Psychological Association between August 11 and September 6, 2011, among 1,226 adults aged 18 and older who reside in the U.S.

In addition to the 1,226 interviews among the general population, oversamples of 300 caregivers and 1,221 people living with chronic illnesses were also included in the 2011 research. For the purposes of this report, caregivers are defined as adults currently caring for an aging or chronically ill family member. Chronically ill adults are defined as those with at least one of the following conditions: depression, type 2 diabetes, obesity and heart disease. In the report, the adults comprising this group are labeled as “Chronic Illness.”

The four generations noted in this report are defined as the following: Millennials (18 – 32 year-olds), Generation X (33 – 46 year-olds), Boomers (47 – 65 year-olds) and Matures (66 years and older).

National results were weighted as needed for age, sex, race/ethnicity, education, region and household income to targets from the Current Population Survey. Data for the caregiver oversample were weighted to the same variables as the national sample using the Centers for Disease Control’s 2009 Behavioral Risk Factor Surveillance System as the population profile. Results for adults with chronic illness were weighted using the same demographic variables as compared to the 2009 National Health Interview Survey. In addition, each condition (depression, diabetes, obesity, heart disease) was weighted as an individual group and then combined, bringing each condition into their proper proportion in the population total. For each of the city reports, results were weighted as needed for age, sex, race/ethnicity, education, region and household income among the entire population within the specific Metropolitan Statistical Area as designated by the U.S. Office of Management and Budget. Propensity score weighting also was used in the weighting of each group to adjust for respondents’ propensity to be online.

All sample surveys and polls, whether or not they use probability sampling, are subject to multiple sources of error, which are most often not possible to quantify or estimate, including sampling error, coverage error, error associated with nonresponse, error associated with question wording and response options, and post-survey weighting and adjustments. Therefore, Harris Interactive avoids the words “margin of error” as they are misleading. All that can be calculated are different possible sampling errors with different probabilities for pure, unweighted, random samples with 100 percent response rates. These are only theoretical because no published polls come close to this ideal. Respondents for this survey were selected from among those who have agreed to participate in Harris Interactive surveys. The data have been weighted to reflect the composition of the U.S. population aged 18 and older. Because the sample is based on those who were invited and agreed to participate in the Harris Interactive online research panel, no estimates of theoretical sampling error can be calculated.