According to the Field Representative's Manual for 1999, this set of GAD questions was included "to determine if the Sample Adult has had or still has a period lasting one month or longer when most of the time they felt worried, tense, or anxious in the past 12 months and, if so, how much they worry, if this worry has ended or is still going on and how long, how long it has affected them, how they dealt with these problems, and how much these problems interfered with their life or activities."

To be asked the Criterion C symptom questions, respondents had to report experiencing a period of feeling worried, tense, or anxious or worrying more than most people that lasted 6+ months. To ascertain this, respondents received a first set of screening questions that asked whether they had experienced a period of feeling worried, tense, or anxious (WOR1MO) or worrying more than most people (WORMORE) during the past 12 months. Respondents who answered "Yes" in either WOR1MO or WORMORE were then given a second set of screening questions used to determine whether this period lasted 6+ months.

For the second set of screening questions, respondents were first asked if the period of feeling worried, tense, or anxious or worrying more than most people was still going on (WORSTILL). Respondents who indicated in WORSTILL that this period had ended were asked, "How many months or years did it go on before it ended?" Responses to this question were recorded in two variables, WORAGONO (number of units) and WORAGOTP (time period). Respondents who indicated in WORSTILL that the period was still going on or who had an unknown answer in WORSTILL were asked about the duration of the (on-going) period of feeling worried, tense, or anxious or worrying more than most people. Their responses to the question "How many months or years has it been going on?" were recorded in two variables, WORNO (number of units) and WORTP (time period). If the respondent's answer to WORAGONO/WORAGOTP or WORNO/WORTP was "unknown," interviewers asked whether the period had lasted at least 6 months (WOR6MO).

They were also asked other Criterion C symptom questions, which included:

• Worried and restless (WORRESTLES)

• Worried and irritable (WORIRRIT)

• Worried and heart raced (WORHEART)

• Worried and easily tired (WORTIRED)

• Worried and having problems sleeping (WORINSOM)

• Worried and dizzy (WORDIZZY)

If respondents answer "Yes" to at least three of the physiological symptom questions, they satisfy the Criterion C element of the scoring system for generalized anxiety disorder caseness, using the NHIS CIDI-SF. To be assigned a probability of caseness for GAD equal to one, respondents must also satisfy requirements for Criterion A (excessive anxiety and worry, occurring more days than not for at least 6 months, about a number of events or activities) and Criterion B (difficult to control the worry). Respondents who reported experiencing at least one physiological symptom of GAD were also asked a series of supplemental questions that inquired about their contact with a medical doctor or other health professional, about their use of medication, drugs, or alcohol, and about how their worry interfered with daily functioning.

For more information on all the variables associated with the NHIS CIDI-SF screening scale on GAD, and for instructions on how to calculate generalized anxiety disorder scores, see WOR1MO.