Reliability and validity of the Portuguese version of the Generalized Anxiety Disorder (GAD-7) scale

Abstract

BackgroundGeneralized anxiety disorder has a strong impact on health-related quality of life. For this reason, it seems relevant to develop strategies allowing early diagnoses in order to promote appropriate treatments. The objective of this study was to culturally adapt and validate the GAD-7 for the Portuguese patients with generalized anxiety disorder.MethodsFor the cultural adaptation of the Portuguese version of the GAD-7 scale we started with a previous translation made by Mapi Institute and decided to perform a clinical review followed by a cognitive debriefing with patients. Once piloted, this version was then tested in a larger sample for feasibility and reliability (1-week test-retest). Construct validity was assessed by the relationship between GAD-7 and socio-demographic and clinical variables. Its unidimensionality was tested by principal component factor analysis. Criterion validity was assessed by comparing GAD-7 scores with those obtained by HADS, and EQ-5D. STAI was mainly used as a screening indicator for patient inclusion.ResultsGAD-7 was considered feasible with a mean completion time of 2.3 minutes and no major floor or ceiling effects. We found an excellent Cronbach’s alpha internal consistency score (0.880) and the test-retest and interclass correlation coefficients were also very good. Regarding the construct validity, younger patients, those with higher education, employed and without anxiety symptoms revealed lower GAD-7 scores, meaning better health. The unidimensionality of GAD-7 index was also confirmed by principal component factor analysis. At last, GAD-7 was significantly correlated with other health outcome indices and the classification levels created by it and by HADS showed to be dependent.ConclusionThe excellent metric properties confirmed the cultural adaptation and validity of GAD-7 into Portuguese population, allowing the clinicians an early detection and treatment of these patients.

Factor structure and construct validity of the Generalized Anxiety Disorder 7-item (GAD-7) among Portuguese college students

“…The relationship with depression is not surprising since GAD has been reported as a predictor of mood disorders 29 , which can later coexist 46 . Comparing the severity bands of GAD-7 with HADS-A bands, just like the recent conclusions by Sousa et al 19 , the classification in this measure was not completely independent. However, distribution differences confirmed in our analysis point to GAD-7 as an equally valid measure to assess anxiety symptoms, but more specifically, to assess symptoms of generalized anxiety disorder.…”

“…Regarding severity categories, we followed the recommendations of the original authors 11 : none/ normal (0 to 5 points), mild (5 to 9 points), moderate (10 to 14 points) and severe (15 to 21 points). The psychometric properties of the GAD-7 Portuguese version 19 were studied using a psychiatric sample with diagnosis of generalized anxiety disorder according to DSM-IV-TR criteria 28 . The GAD-7 presented a one-dimensional structure and good internal consistency (α = 0.88).…”

“…As a short and objective self-report measure showing strong properties as a screening tool 11 , researchers have tested its psychometric characteristics in several settings. In this context, over the last decade, GAD-7 has been presented as a reliable and valid questionnaire in different languages 14,15,16,17,18 including Portuguese 19 , with heterogeneous psychiatric samples 20,21 for specific medical conditions 22,23,24,25 in the general population 26 and in geriatric samples 27 . However, the one-dimensional nature of GAD-7 proposed by the original model is not consistent in the literature.…”

Exercise-Induced Change in Plasma IL-12p70 Is Linked to Migraine Prevention and Anxiolytic Effects in Treatment-Naïve Women: A Randomized Controlled Trial

“…Anxiety was assessed by a 7-item General Anxiety Disorder (GAD-7) scale. The GAD-7 scale screens typical anxiety-related indicators experienced in the previous 2 weeks, and has been validated and translated into Brazilian Portuguese [28]. …”

The validation of the Serbian version of the general anxiety disorder scale (GAD7): A pilot study

“…Out of the original 13 items that covered all of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) symptom criteria for GAD and items created on the basis of review of existing anxiety scales [11] . The screener was later standardized on the general population [10] , and has since been translated and standardized in many languages and cultures such as Spanish [12] , Portugese [13] and others. Because of its shortner and constant crosscultural reliability this scale is considered optimal for degermining the existance and the severity of GAD.…”