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."

The periodic mental health section of the 1999 NHIS includes questions taken from the CIDI-SF screening scales for major depression, generalized anxiety disorder, and panic attacks. More information on the major depression questions--for dysphoric mood and for anhedonia, respectively--can be found in DEP2WKEV and DEPLIFUN. For more information on the panic attack questions, see PANICYR.

WOR1MO (Felt worried/tense/anxious most of the time for 1+ months in the past 12 months) is the first screening question asked. Respondents who answer "No" and those with an unknown answer to WOR1MO receive an additional question:

Respondents who answer "Yes" to either WOR1MO or WORMORE receive a second set of screening questions that inquire about the duration of the period of feeling worried, tense, or anxious or worrying more than most people. The first screening question in this series asks, "Has that period ended or is it still going on?" (WORSTILL). If respondents indicate that the period had ended, they are then asked, "How many months or years did it go on before it ended?" Responses to this question were recorded in two variables, WORAGOTP, which reports the time unit (months or years), and WORAGONO, which reports the number of such time units mentioned.

Respondents who indicate that the period of feeling worried, tense, or anxious or worrying more than most people is still going on and those with an unknown answer to WORSTILL are then asked about the duration of this (on-going) period. Their responses to the question, "How many months or years has it been going on?" were recorded in two variables, WORTP, which reports the time unit (months or years), and WORNO, which reports the number of such time units mentioned.

If a specific answer about the duration of feeling worried, tense, or anxious or worrying more than most people cannot be elicited (IPUMS NHIS codes 7, 8, or 9 in WORAGONO, WORAGOTP, WORNO, or WORTP), interviewers ask, "[Did it last/Has it been] at least 6 months?" (WOR6MO).

Eliciting information about the duration of the period of feeling worried, tense, or anxious or worrying more than most people is important because only respondents who (1) pass one of the first two screening questions (WOR1MO or WORMORE) and (2) indicate this period lasted at least 6 months (in WORAGONO/WORAGOTP or WORNO/WORTP or WOR6MO) receive further questions related to GAD. The follow-up questions in the NHIS CIDI-SF relating to symptoms of GAD are discussed in the next section.

The public use files of the NHIS include two summary recoded variables indicating the duration of the period of feeling worried, tense, or anxious or worrying more than most people, using a single time unit of years. These recoded variables are WORAGOYR (a recode of WORAGONO and WORAGOTP) and WORYR (a recode of WORNO and WORTP). While these variables may be useful to researchers as stand-alone variables, they are not used in the scoring system for determining the probability of caseness for GAD (a topic discussed in a later section).

The DSM-IV criteria for diagnosis of GAD include:

• Criterion A: Excessive anxiety and worry, occurring more days than not for at least 6 months, about a number of events or activities

• Criterion B: Difficult to control the worry

• Criterion C: Anxiety and worry associated with three or more physiological symptoms

• Criterion D: Anxiety and worry are not features of other related disorders, such as panic disorder, social phobia, obsessive-compulsive disorder, and anorexia nervosa

• Criterion E: Anxiety, worry, or physical symptoms cause significant distress or impairment

• Criterion F: Disturbance not due to direct physiological effects of a substance or a general medical condition and does not occur exclusively during a Mood Disorder, a Psychotic Disorder, or a Pervasive Developmental Disorder

Variables related to Criterion A include:

• Worry stronger than most people for 6+ months (WORSTRONG)

• Worry most days (WORMOSTDAY)

• Worry about one particular thing (WORONE)

• Have different worries at once (WORMANY)

Variables related to Criterion B include:

• Difficult to stop worrying (WORNOSTOP)

• Can't put worries out of mind (WORCANTPUT)

• Can't control worries (WORCONTROL)

Five of the seven physiological symptoms referred to in the NHIS instrument are:

• Worried and restless (WORRESTLES)

• Worried and keyed up/on edge (WOREDGY)

• Worried and irritable (WORIRRIT)

• Worried and easily tired (WORTIRED)

• Worried and having problems sleeping (WORINSOM)

The NHIS CIDI-SF omits two physiological symptoms that were part of the DSM-IV's Criterion C ("muscle tension" and "difficulty concentrating or mind going blank") and instead includes two symptoms that were part of the DSM-III's criteria for diagnosing GAD. These symptoms were:

• Worried and heart raced (WORHEART)

• Worried and dizzy (WORDIZZY)

The DSM-IV's GAD Criterion D (anxiety and worry are not features of other related disorders) is represented by an additional symptom question, "What sorts of things [did/do] you mainly worry about?" However, responses to this question were not included in the public use files of the NHIS.

According to the WHO CIDI-SF scoring guide, the DSM-IV's GAD Criterion E (anxiety, worry, or physical symptoms cause significant distress or impairment) is evaluated by the endorsement of criteria A and B, above. Criterion F (disturbance is not due to the direct physiological effects of substance or a general medical condition and does not occur exclusively during a Mood Disorder, a Psychotic Disorder, or a Pervasive Development Disorder) is not evaluated in the WHO or the NHIS CIDI-SF instruments. Scoring of the NHIS CIDI-SF for GAD is discussed in a later section.

These supplemental questions are:

• Told doctor about worries (WORTOLDDR)

• Told health professional about worries (WORTOLDHP)

• Used medication/drugs/alcohol to cope with worries (WORDRUGALC)

• Amount worry interfered with life (WORINTFERE)

First, in the WHO CIDI-SF, respondents who answer "No" to WOR1MO (Felt worried/tense/anxious most of the time for 1+ months, past 12 months) receive the follow-up question associated with WORMORE (Worried more than most people, past 12 months. In the NHIS CIDI-SF, respondents who answered "No" in WOR1MO and those who had an "unknown" answer (IHIS codes 7, 8, 9) were asked the question associated with WORMORE.

A second difference between the WHO and NHIS CIDI-SF instruments concerns the screening question WORSTILL (Has period of worry ended). In the WHO CIDI-SF, respondents had to indicate in WORSTILL whether the period of feeling worried, tense, or anxious or worrying more than most people had "Ended" or was "Still Going On" to receive further questions inquiring about the duration of this period. In the NHIS CIDI-SF respondents who had an "unknown" answer in WORSTILL (IHIS codes 7, 8, 9) were also asked further questions about the duration of this period. Respondents with an "unknown" answer in WORSTILL were grouped with those who said this period was still going on and were asked, "How many months or years has it been going on?," with answers recorded in WORTP and WORNO and recoded in WORYR.

A third screening question, WOR6MO (Period of worry lasted 6+ months), also differed between the WHO and NHIS CIDI-SF instruments. In the WHO CIDI-SF instrument, respondents were only asked about the duration of their period of feeling worried, tense, or anxious or worrying more that most people through the questions associated with WORAGONO/WORAGOTP and WORNO/WORTP. The NHIS CIDI-SF instrument, however, includes an additional question, "[Did it last/Has it been] at least 6 months?" (WOR6MO), that was asked of respondents for whom the duration of feeling worried, tense, or anxious or worrying more than most people was unknown (IHIS codes 7, 8, and 9 in WORAGONO, WORAGOTP, WORNO or WORTP).

Two of the physiological symptoms included in the NHIS CIDI-SF, "Worried and heart raced" (WORHEART) and "Worried and dizzy" (WORDIZZY), were taken from the DSM-III and were not included in the WHO CIDI-SF. In contrast, two of the physiological symptoms included in the WHO CIDI-SF, "difficulty keeping your mind of what you (were/are) doing" and having "tense, sore, or aching muscles," were taken from the DSM-IV and were not included in the NHIS CIDI-SF.

Finally, in the WHO CIDI-SF instrument, respondents had to answer "Yes" to at least two questions about physiological symptoms to receive the supplemental questions. In the NHIS CIDI-SF, by contrast, respondents had to answer "Yes" to only one question about physiological symptoms to be asked supplemental questions.

According to the Appendix on Adult Mental Health Documentation included in the 1999 NHIS Survey Description, the "NCHS suggests that individual CIDI-SF items not be used for purposes beyond those recommended by the World Health Organization (WHO)." The Survey Description then directs users to the WHO's website for instructions on how to calculate the probability of psychiatric diagnosis based on responses to individual NHIS CIDI-SF items.

For GADCDC, a score of one indicates that respondents met the CIDI-SF criteria for caseness of GAD; a score of zero indicates that they did not meet these criteria. The scoring system described below follows the scoring procedure implemented in research conducted by the Department of Health and Human Services, which used NHIS CIDI-SF GAD question responses to calculate the probability of caseness for GAD (See http://www.hcp.med.harvard.edu/ncs/ftpdir/cidisf_readme.pdf).

Respondents must report experiencing a period of feeling worried, tense, or anxious or worrying more than most people during the past 12 months (a "Yes" in WOR1MO or a "Yes" in WORMORE) and must report that this period lasted 6 months or more (based on answers to the questions associated with WORAGONO/WORAGOTP or WORNO/WORTP or WOR6MO) to receive further questions on symptoms of GAD. Respondents who do not pass both sets of screening questions receive a score of 0 (zero probability of psychiatric caseness for GAD) in GADCDC.

Respondents who pass both sets of screening questions and go on to answer the GAD symptom questions only receive a probability of caseness equal to one if they report experiencing symptoms, as specified below, in each of the first three DSM-IV criterion groups (A, B, C).

To meet the Criterion A requirements, respondents needed to indicate that their period of feeling worried, tense, or anxious or worrying more than most people was excessive, lasted more days than not, and involved worrying about more than one thing. These requirements were met if respondents answered in the affirmative to WORSTRONG (Worry stronger than most people for 6+ months) and WORMOSTDAY (Worry most days), as well as answered "No" in WORONE (Worry about one particular thing) or "Yes" in WORMANY (Have different worries at once).

For the Criterion B requirement (lack of control), respondents needed to indicate that either (a) it was difficult to stop worrying (a "Yes" in WORNOSTOP), (b) their worry was often so strong that they couldn't put it out of their minds (according to WORCANTPUT), or (c) it was often difficult to control their worry (according to WORCONTROL).

Finally, to meet the Criterion C requirements, respondents needed to answer "Yes" to at least three of the following physiological symptom questions:

• Worried and restless (WORRESTLES)

• Worried and keyed up/on edge (WOREDGY)

• Worried and irritable (WORIRRIT)

• Worried and heart raced (WORHEART)

• Worried and easily tired (WORTIRED)

• Worried and having problems sleeping (WORINSOM)

• Worried and dizzy (WORDIZZY)

Only respondents who meet all of these requirements (passing the screening questions and meeting Criteria A, B, and C as specified above) are assigned a probability of psychiatric caseness equal to one (i.e., a value of 1 in GADCDC). Sample adults who do not meet all of these requirements are assigned a probability of psychiatric caseness equal to zero (i.e., a value of 0 in GADCDC).