Psychometric properties of the Strengths and Difficulties Questionnaire in an Icelandic community sample

The current paper aimed to evaluate the psychometric properties of the Icelandic translation of the Strengths and Difficulties Questionnaire, for both parent and teacher reports. SDQ is a widely used questionnaire for screening mental problems among youth. However, only a few studies have conducted a factor analysis on the youngest and oldest cohorts using an adequate sample size. This study aims not only to examine the traditional 5-factor model and alternative models suggested in prior research but also to establish norm data for the Icelandic population.

The total sample consists of 1653 youth aged 5-16 years, thereof 316 parent reports and 271 teacher reports for the 5-year-old sample. We used confirmatory factor analysis to evaluate the factor structure. Special attention was given to the models' performance across different age groups and between genders. This cross-demographic evaluation is vital to ensure that the SDQ's utility is not limited by developmental or gender-specific variations in symptom expression or reporting.

We found an acceptable fit for both the original five-factor model and the more recent three-factor model with higher-order internalizing and externalizing factors. The fit for the factor structures seemed to be quite similar across ages. However, we observed goodness-of-fit below the acceptable range for girls on the parent ratings. We also found evidence for the convergent and divergent validity of both models.

The current study provides further evidence of the utility of the SDQ as a screening instrument, with an acceptable factor structure across ages.