Dataset Information

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.

ABSTRACT:

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.

SUBMITTER: Tomitaka S

PROVIDER: S-EPMC8461873 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:The dimensionality of depression and anxiety instruments have recently been a source of controversy. OBJECTIVES AND DESIGN:In a European-wide sample of patients after Traumatic Brain Injury (TBI), we aim to examine the factorial structure, validity, and association of the Patient Health Questionnaire for depression (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) instruments. This study is based on longitudinal observational data. We conducted analyses of factorial structure and discriminant validity of outcomes six-months after TBI. We also examined the prevalence, co-occurrence, and changes of scores on the PHQ-9 and GAD-7 at 3-, 6-, and 12-month post-TBI assessments. PARTICIPANTS:At six-months post-TBI assessment, 2137 (738 (34.5%) women) participants completed the PHQ-9 and GAD-7 questionnaires. For the longitudinal analysis, we had 1922 participants (672 (35.0%) women). RESULTS:The results of exploratory factor analysis suggested a general latent construct underlying both PHQ-9 and GAD-7 measures. Confirmatory factor analyses showed a slight improvement in the fit indices for the bifactorial model. The Omega hierarchical test clearly differentiated two subfactors of PHQ-9 and GAD-7 items over and above the underlying general factor; however, most of the variance (85.0%) was explained by the general factor and the explained variance of the subfactors was small. The PHQ-9 and GAD-7 performed similarly in detecting post-traumatic stress disorder (PTSD). As defined by conventional cut-offs, depression and anxiety have different prevalence rates in the sample. The scales also differed in their relationships with the short form of health survey (SF-36v2) subscales. The longitudinal analysis showed high stability of depression and anxiety symptoms: 49-67% of the post-TBI patients with comorbid depression and anxiety reported the persistence of the symptoms over time. DISCUSSION:The factorial structure analysis favors a general latent construct underlying both depression and anxiety scales among patients after TBI. We discuss the implications our findings and future research directions.