Objective: To examine the psychometric properties of the Strengths and Difficulties Questionnaire (SDQ) parent version and to determine the effects of age, gender, country and investigator type (paediatrician, child psychiatrist, other physician) on the SDQ scores in the prospective, non-interventional ADORE study.
Methods: The SDQ was completed for 1,459 children with ADHD (aged 6-18 years) in 10 European countries.
Results: Factor analysis provided an exact replication of the original 5-factor SDQ subscale structure. All subscales were sufficiently homogeneous. The mean total difficulties and SDQ subscale scores of the ADORE sample clearly differed from UK normative data. Younger children were more impaired on different SDQ scales than older children, and girls were more emotionally affected than boys. Differences between countries were found for each SDQ scale, but the investigator type had no significant effect. Correlation coefficients between SDQ scales and other scales used in ADORE ranged from low (r<0.30) to high (r>0.50).
Conclusions: The present study confirmed the validity and reliability of the parent-reported SDQ scale structure and showed that the scale scores are dependent on age and gender. In contrast to investigator type, different cultures had a significant effect on SDQ scores. Correlations with other scales used in the ADORE study underline both separate domains and meaningful associations.