Specifically, Kessler's instrument asks how often, during the past 30 days, the respondent felt:

• So sad that nothing could cheer you up? (ASAD)

• Nervous? (ANERVOUS)

• Restless or fidgety? (ARESTLESS)

• Hopeless? (AHOPELESS)

• That everything was an effort? (AEFFORT)

• Worthless? (AWORTHLESS)

For each of these questions, respondents selected one of the following responses from a flashcard: "none of the time," "a little of the time," "some of the time," "most of the time," "all of the time."

Sample adults who responded "some of the time," "most of the time," or "all of the time" to any of these questions were asked about how such feelings interfered with their lives. Specifically, interviewers asked, "Altogether, how much did these feelings interfere with your life or activities: a little, some, a lot, or not at all?" Those who answered "a little," "some," or "a lot" were asked about how many days during the last 30 days they were totally unable to work or carry out their usual activities (FBADUNABLE). Those who reported a number lower than 30 were asked the aforementioned question for FBADCUTDOWN. These follow-up questions were not part of the tool designed by Kessler to measure nonspecific psychological distress or severe mental illness.