Reliability and validity of the Strengths and Difficulties Questionnaire in Greek adolescents and their parents

The Strengths and Difficulties Questionnaire (SDQ) is a brief screening measure of emotional and behavioural difficulties in children and adolescents. The aim of this study was to assess reliability and validity of the Greek version of the SDQ. A representative Greek sample of 1194 adolescents (aged 11 to 17 years) and their parents completed the SDQ along with other measures. Internal consistency reliability was determined by calculation of the Cronbach α coefficient. Varimax Orthogonal Transformation was conducted to test the factor structure of the questionnaire. Validity was further examined by investigating the correlation of the SDQ with the KIDSCREEN questionnaire and its association with demographic factors. The inter-rater agreement between parent and self-reports was analyzed with Pearson’s correlation coefficient. Intra-class correlation coefficients (ICCs) were computed to determine test-retest stability. For both parent and the self-report SDQ versions, most items loaded onto their predicted factors in consistency with the originally proposed five-factor structure. Internal consistency reliability was acceptable with a Cronbach α above 0.70 for all SDQ scales except for conduct and peer problems. Inter-rater correlations ranged from 0.33 to 0.45. Test-retest stability was good (ICCs > 0.60). Correlation coefficients between the SDQ and KIDSCREEN questionnaire were significant. Small effect sizes (d > 0.5) of the socioeconomic status were found for all of the SDQ scale mean scores. In conclusion, the SDQ was found to have satisfying psychometric properties and could be suitable for assessing emotional and behavioural problems in Greek adolescents.