Psychometric properties of the Brief Symptom Inventory in nomophobic subjects: insights from preliminary confirmatory factor, exploratory factor, and clustering analyses in a sample of healthy Italian volunteers

Background: The Brief Symptom Inventory (BSI), developed by Derogatis in 1975, represents an important standardized screening instrument that enables one to quantitatively assess psychological distress and psychiatric disorders. The BSI is a 53-item self-report scale, measuring nine dimensions that can be summed up to reflect three global indices, including the General Severity Index (GSI). In the era of new information and communication technologies, nomophobia ("no mobile phobia") is an emerging disorder, characterized by the fear of being out of mobile phone contact. Nothing is known, however, about the factor structure and reliability of the BSI in a population of nomophobic subjects. This study aimed at addressing this gap in knowledge. Methods: A sample of 403 subjects aged 27.91 +/- 8.63 years (160 males, 39.7% of the entire sample, and 243 females, 60.3%), recruited via snowball sampling, volunteered to take part in the study. The Italian versions of the Nomophobia questionnaire and the BSI were administered. Exploratory factor analyses, confirmatory factor analyses, and clustering analysis were carried out together with correlation analysis, analysis of variance, and multivariate regression analysis. Results: For each BSI subscale, scores were significantly higher than the norms. The nine subscales exhibited acceptable-to-good Cronbach's alpha coefficients, varying from 0.733 for psychoticism to 0.875 for depression. Overall, the reliability of the entire instrument proved to be excellent (alpha coefficient=0.972). Furthermore, all BSI subscales as well as BSI synthetic indexes correlated with nomophobia in a significant way. Stratifying the population according to the severity of nomophobia (mild, 206 individuals, 51.1% of the sample; moderate, 167 subjects, 41.4%; and severe, 30 individuals, 7.4%), the GSI score could distinguish (P<0.001) between mild and moderate (0.99 +/- 0.71 vs 1.32 +/- 0.81) and between mild and severe (0.99 +/- 0.71 vs 1.54 +/- 0.79) nomophobia, although not between moderate and severe nomophobia (P>0.05). Similar patterns could be found for the other subscales of the BSI. Finally, looking at the fit indexes, the second-order 9-factor model best fit the data compared with the Derogatis 1-factor model. Conclusion: The findings of our study show that the BSI is a reliable and valid instrument with acceptable psychometric properties, and can be administered to populations of nomophobic subjects.