Validation of General Anxiety Disorder (GAD-7) questionnaire in Spanish nursing students

Design

A cross-sectional descriptive study was carried out during March–May 2022 at the University of Jaen (Spain) to validate the General Anxiety Disorder (GAD-7) questionnaire in university nursing students.

Sample selection

The study population was students enrolled in the Nursing Degree at the University of Jaen. As an inclusion criterion, the students had to be enrolled in the first or second year in 2022 and excluded third and four years students, as higher courses seem to cope better with anxiety (Gupta, Anupama & Ramakrishna, 2021).

The criteria for carrying out a factorial analysis were used to calculate the sample size. These criteria contemplate 10 subjects for each item (De Vet et al., 2005); therefore, a sample of at least 70 participants was needed.

Information source and variables

A self-administered online questionnaire was used that was made available to the students in the first or second year of the nursing degree. Sociodemographic variables and characteristics of the university profile of university students were collected. This questionnaire also included two scales that assessed anxiety: The Generalized Anxiety Disorder Scale (GAD-7) and the Goldberg anxiety subscale. The former comprises seven items and was designed by Löwe et al. (2008). It has a high internal consistency and has been culturally adapted in the Spanish context and used among nursing students and other health degrees in other countries (Alonso et al., 2021; Bártolo, Monteiro & Pereira, 2017; Dhira et al., 2021; Eisenberg et al., 2007; Hinz et al., 2017; Lun et al., 2018; Zhang et al., 2021).

The GAD questionnaire consists of seven items (“Feeling nervous, anxious, or on edge?”, “Not being able to stop or control worrying?”, “Worrying too much about different things?”, “Trouble relaxing?”, “Being so restless that it is hard to sit still?”, “Becoming easily annoyed or irritable?” and “Feeling afraid as if something awful might happen?”), with four response options each, where each item scores from 0–3, with 21 being the maximum score, and the presence of mild symptoms detected from five points. This tool allows screening for the presence of generalized anxiety disorder (Löwe et al., 2008). The scale designed by Goldberg et al. was used to determine convergent validity (Goldberg et al., 1988). This scale has been adapted to the Spanish cultural context and has been previously used in our cultural context (Montón et al., 1993) and also in other countries among nursing students (Luo et al., 2019). For this purpose, only the first nine items are included, belonging to the Anxiety subscale (Goldberg et al., 1988).

Statistical analysis

All statistical analyzes have been performed with SPSS version 24.0 (IBM SSPS, Armonk, NY, USA).

The absolute and relative frequencies were used to describe the qualitative variables, and the mean and standard deviation (SD) to describe the quantitative variables of the sociodemographic data and university profile.

An exploratory factor analysis (EFA) was chosen for construct validity to determine the underlying factors through a principal component analysis (PCA), and was used to explore the set of latent variables or common factors that explain the answers to the items of a test. Before performing the EFA, we analyzed the Kaiser-Meyer-Olkin (KMO) tests and the Bartlett sphericity tests to determine if it was appropriate to apply this analysis. For this to be the case, the KMO must be above 0.6 and as close as possible to 1, and the Bartlett sphericity, which consists of the statistical hypothesis test, must present a p-value less than 0.05 to reject the hypothesis null of sphericity and ensure that the factorial model is adequate to explain the data.

In the EFA, we used the Varimax rotation, and the kaiser criterion was used to determine the number of factors to retain, one of the most used criteria. Factors with eigenvalues greater than the unit value were retained.

Within the construct validity, we also analyze the convergent validity through the Pearson correlation coefficient between the GAD scale and Goldberg Scale scores and the relationship between the GAD scale scores with the academic year and other sociodemographic and university profile factors. The results were considered statistically significant when p ≤ 0.05. We also analyzed the GAD scale’s predictive capacity on high anxiety scores (Scores >or  = 4 points) of the Goldberg scale using the area under the ROC curve. The reliability analysis was performed using the Cronbach test (α) to assess internal consistency (IC). The IC indicates to what extent the questionnaire items correlate and how they fit together and measure the same concept. The α is one of the most used measures to evaluate the reliability of a scale (Streiner, Norman & Cairney, 2015; Tabachnick & Fidell, 2013). Its values range from 0 to 1. One of the most accepted rules is to consider α > 0.9 as excellent, α > 0.8 as good, α > 0.7 as acceptable, α > 0.6 as questionable, α > 0.5 as poor, and α < 0.5 as unacceptable.

Ethical considerations

For the collection of information, approval has been obtained from the Research Ethics Committee of the University Jaen, APR.22/3.PRY. All participants had to read the instructions and freely accept an ad-hoc informed consent before beginning to complete the questionnaire. The data was handled in a disaggregated manner, and the anonymity of the participants was maintained at all times.

Characteristics of the study subjects

A total of 170 university nursing students participated. The mean age was 22.1 years (SD = 7.03). Of these 170, 82 were enrolled in the first year and 88 in the second year of the degree. The majority (84.7%) were women (144). Most (130, 76.5%) had chosen nursing as their first option for university education (62 in the first year and 68 in the second year). 63.5% (108) had a scholarship at the time of the study. 83.5% (142) had no previous experience in the clinical setting. The most common reason for choosing nursing was vocation (67.6%, 115), followed by the future options that the degree provides (17.1%, 29).

Most first-year students had suffered an anxiety crisis (shortness of breath, palpitations, chest pressure, dizziness, and fear of losing control or dying) on some occasion (74.4%, 61), while slightly fewer second-year students have presented these anxiety crises (59.1%, 52). Further information that characterizes the sample can be found in Table 1.

Exploratory factor analysis

The KMO test presented a value of 0.909, and the Bartlett sphericity test was <0.01. Therefore, an EFA was carried out. A single component that contained the 7 items explained 63.50% of the variance. Figure 1 shows the scree plot of eigenvalues with the Kaiser rule. In addition, all anti-image diagonal correlations showed figures higher than 0.884. Table 2 presents the scale items together with their respective factorial weights.

Convergent validity and relationship with other sociodemographic and university profile variables.

The Goldberg anxiety subscale was used for the convergent validity analysis, showing a statistically significant correlation with the GAD-7 scale (r = 0.653; p < 0.001). Next, the relationship between different sociodemographic and university profile variables was studied with the GAD-7 scale, observing a statistically significant association with the academic year, gender, and having experienced an anxiety crisis. First-year students, women, and students with a previous anxiety crisis presented higher scores on the GAD-7 (Table 3). Regarding the predictive capacity of the GAD-7 scale for high scores of the Goldberg scale, an excellent predictive capacity was found with an area under the ROC curve of 0.91 (95% CI [0.86–0.96]) Figure 2.

Internal consistency

For the total scale, the value of α was 0.903. All alpha values scored above 0.884 when removing an item. The α values for each factor are shown in Table 4.