Factor structure of the SDQ and longitudinal associations from pre-school to pre-teen in New Zealand.

The factor analysis shows that the Strengths and Difficulties Questionnaire has a similar factor structure, particularly in older ages, to that previously published and shows good internal consistency. At the pre-school follow up, a larger than expected proportion of children were identified with high scores, particularly in the conduct sub-scale. Children's behaviour changes over time, with only poor to moderate agreement between those identified as abnormal or borderline over the longitudinal follow up.