The GAD-7 and the PHQ-8 exhibit the same mathematical pattern of item responses in the general population: analysis of data from the National Health Interview Survey

[Background] Recent studies have shown that, among the general population, responses to depression-rating scales follow a common mathematical pattern. However, the mathematical pattern among responses to the items of the Generalized Anxiety Disorder-7 (GAD-7) is currently unknown. The present study investigated whether item responses to the GAD-7, when administered to the general population, follow the same mathematical distribution as those of depression-rating scales. [Methods] We used data from the 2019 National Health Interview Survey (31, 997 individuals), which is a nationwide survey of adults conducted annually in the United States. The patterns of item responses to the GAD-7 and the Patient Health Questionnaire-8 (PHQ-8), respectively, were analyzed inductively. [Results] For all GAD-7 items, the frequency distribution for each response option (“not at all, ” “several days, ” “more than half the days, ” and “nearly every day, ” respectively) was positively skewed. Line charts representing the responses to each GAD-7 item all crossed at a single point between “not at all” and “several days” and, on a logarithmic scale, showed a parallel pattern from “several days” to “nearly every day.” This mathematical pattern among the item responses was identical to that of the PHQ-8. This characteristic pattern of the item responses developed because the values for the “more than half the days” to “several days” ratio were similar across all items, as were the values for the “nearly every day” to “more than half the days” ratio. [Conclusions] Our results suggest that the symptom criteria of generalized anxiety disorder and major depression have a common distribution pattern in the general population

A distribution model of the responses to each depressive symptom item in a general population: A cross-sectional study

Objective: Some researchers have reported that distribution of total depressive symptom scores in the general population may follow an exponential pattern except at the lowest end of the scores. To understand the mechanism responsible for this phenomenon, we investigated the mathematical patterns of the individual distributions for each item of a depressive symptom scale. Methods: We analysed data from 32 022 participants in the general population who participated in the Active Survey of Health and Welfare, Japan. Depressive symptoms were assessed using the Japanese version of Center for Epidemiologic Studies Depression Scale (CES-D). CES-D has 20 items, each of which is scored in 4 grades: 'Rarely', 'Some', 'Much' and 'Most of the time'. Results: The individual distributions of 16 negative items belonging to the depressive mood, somatic symptoms and retarded activities, and interpersonal relations categories, followed a common mathematical pattern, which displayed different distributions with a boundary at 'Some'. The distributions for the 16 items between 'Rarely' and 'Some' appeared to cross at a single point. On the other hand, the distributions of the 16 items between 'Some' and 'Most' followed a linear pattern when plotted using a log-normal scale. The remaining 4 items in the positive affect subscale showed non-specific patterns. Conclusions: The common mathematical pattern of the 16 negative item distributions may contribute to the exponential pattern of the distribution of total depressive symptom scores except at the lowest end of the scores

Responses to depressive symptom items exhibit a common mathematical pattern across the European populations

The theoretical distribution of responses to depressive symptom items in a general population remains unknown. Recent studies have shown that responses to depressive symptom items follow the same pattern in the US and Japanese populations, but the degree to which these findings can be generalized to other countries is unknown. The purpose of this study was to conduct a pattern analysis on the EU population’s responses to depressive symptom items using data from the Eurobarometer. The Eurobarometer questionnaires include six depressive symptom items from the 12-item General Health Questionnaire. The pattern analysis revealed that, across the entire EU population, the ratios between “score = 2” and “score = 1” and between “score = 3” to “score = 2” were similar among the six items and resulted in a common pattern. This common pattern was characterized by an intersection at a single point between “score = 0” and “score = 1” and a parallel pattern between “score = 1” and “score = 3” on a logarithmic scale. Country-by-country analyses revealed that the item responses followed a common characteristic pattern across all 15 countries. Our results suggest that responses to depressive symptom items in a general population follow the same characteristic pattern regardless of the specific country

Stability of the Distribution of Patient Health Questionnaire-9 Scores Against Age in the General Population: Data From the National Health and Nutrition Examination Survey

Background: Epidemiological studies using the nine-item Patient Health Questionnaire (PHQ-9) have reported inconsistencies regarding the relationship between age and total scores. To determine whether this discrepancy is due to the stability of the distribution of PHQ-9 total scores against age, we investigated whether the total score distribution remains stable during adulthood, and also investigated the mathematical patterns of the total score distribution.Methods: The present study utilized data from 15,847 participants of the 2009–2014 United States National Health and Nutrition Examination Survey, all of whom responded to all PHQ-9 items. The stability of the total score distribution among different age groups was examined using overlap coefficients and graphical analysis.Results: High overlap coefficients were observed between all age groups for the distributions of PHQ-9 total scores, suggesting that the distribution of PHQ-9 total scores remains stable against age. Graphical analysis demonstrated that distributions of PHQ-9 total scores were similar across age groups. In addition, distributions of PHQ-9 total scores exhibited an exponential pattern, except at the lower end of the distribution.Conclusions: Our findings indicate that the stability of the distribution of PHQ-9 total scores throughout adulthood may underlie inconsistencies in the evidence regarding age-related changes in total depression scores

Item Response Patterns on the Patient Health Questionnaire-8 in a Nationally Representative Sample of US Adults

Recent studies have shown that item responses on the Center for Epidemiologic Studies Depression Scale (CES-D) and Kessler Screening Scale for Psychological Distress (K6) exhibit the same characteristic item response patterns among the general population. However, the distributional patterns of responses on the Patient Health Questionnaire-8 (PHQ-8) among the general population have not been adequately studied. Thus, we conducted a pattern analysis of PHQ-8 item responses among US adults. Data (18,446 individuals) were obtained from the 2015 Behavioral Risk Factor Surveillance Survey (BRFSS). Item responses on the BRFSS version of the PHQ-8 were scored using the number of days response set and then converted to the original 4-point scale. The patterns of item responses were analyzed through graphical analysis. Lines of item responses scored using the number of days response set showed the same pattern among the eight items, characterized by crossing at a single point between “0 days” and “1 day,” and parallel fluctuation from “1 day” to “14 days” on a semi-logarithmic scale. Lines of item responses converted to the 4-point scale also showed the same characteristic pattern among the eight items. The present results demonstrate that the item responses on the PHQ-8 show the same characteristic patterns among items, consistent with the CES-D and the K6

Age-related changes in the distributions of depressive symptom items in the general population: a cross-sectional study using the exponential distribution model

Background. Previous research has reported inconsistent evidence of the trajectory of depressive symptoms across the adult lifespan. We investigated how the distributions of each item score change with age and determined whether the trajectory of depressive symptoms varied with the scoring methods of the questionnaire. Methods. We analyzed data collected from 21, 040 subjects who participated in the national survey in Japan. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D has 20 items, each of which is scored in four grades of "rarely, " "some, " "much, : and "most of the time." We used the exponential distribution model which fits the distributions of 16 negative symptom items of CES-D, with the probabilities of "some, " "much, " "most, " and "rarely" expressed as P, Pr, Pr2, and 1-P×(r2Cr C1). Results. The distributions of the responses to 16 negative symptom items followed the common exponential model across all age groups. The mean of the estimated parameter r of 16 negative items showed a U-shape pattern, being high during 12-29 years, remaining low during 30-50 years, and then increasing again over 60 years. The trajectory of depressive symptom scores simulating the binary method was different from that of the empirical scores using the Likert method. Conclusions. Our findings show that the increase in the depressive symptoms score during older age is based on the increase of the parameter r. The differences in the scoring method may contribute to the different age-related patterns across the adult lifespan

Relationship between item responses of negative affect items and the distribution of the sum of the item scores in the general population

Background: Several studies have shown that total depressive symptom scores in the general population approximate an exponential pattern, except for the lower end of the distribution. The Center for Epidemiologic Studies Depression Scale (CES-D) consists of 20 items, each of which may take on four scores: "rarely, " "some, " "occasionally, " and "most of the time." Recently, we reported that the item responses for 16 negative affect items commonly exhibit exponential patterns, except for the level of "rarely, " leading us to hypothesize that the item responses at the level of "rarely" may be related to the non-exponential pattern typical of the lower end of the distribution. To verify this hypothesis, we investigated how the item responses contribute to the distribution of the sum of the item scores. Methods: Data collected from 21, 040 subjects who had completed the CES-D questionnaire as part of a Japanese national survey were analyzed. To assess the item responses of negative affect items, we used a parameter r, which denotes the ratio of "rarely" to "some" in each item response. The distributions of the sum of negative affect items in various combinations were analyzed using log-normal scales and curve fitting. Results: The sum of the item scores approximated an exponential pattern regardless of the combination of items, whereas, at the lower end of the distributions, there was a clear divergence between the actual data and the predicted exponential pattern. At the lower end of the distributions, the sum of the item scores with high values of r exhibited higher scores compared to those predicted from the exponential pattern, whereas the sum of the item scores with low values of r exhibited lower scores compared to those predicted. Conclusions: The distributional pattern of the sum of the item scores could be predicted from the item responses of such items

CES-D distributions for the middle adulthood group (A), the young adulthood group (B), and the older age group (C).

<p>CES-D distributions for the middle adulthood group (A), the young adulthood group (B), and the older age group (C).</p

Summary of descriptive statistics for the CED-D distribution in the general Japanese population according to age group.

<p>Summary of descriptive statistics for the CED-D distribution in the general Japanese population according to age group.</p