Technical Report based on the Strengths and Difficulties Questionnaire (SDQ)

SDQ scores are dimensions (like height, weight or IQ), and the likelihood of current or future psychological difficulties rises steadily with each one point increase in score. For ease of interpretation, we simplify by grouping SDQ scores into four bands so that in the general population roughly 80% of young people score 'close to average', 10% score 'slightly raised', 5% score 'high' and 5% score 'very high'. The exception is the scale for kind and helpful behaviour, with roughly 80% 'close to average', 10% 'slightly low', 5% 'low' and 5% 'very low'.

Some young people have recognised patterns of psychological difficulties that have a major impact on the young person's wellbeing - these patterns of difficulties correspond to what ICD-10 and DSM-5 recognise as disorders. Such young people may benefit from expert assessment and help. Based on the questionnaire scores, we can predict whether young people are at 'low risk', 'medium risk' or 'high risk'. In general, these predictions agree fairly well with what an expert would say after a detailed psychological assessment of the young person. Around 25-60% of young people who are rated as high risk do turn out to have a relevant ICD-10/DSM-5 disorder according to experts. So do around 10-15% of young people at medium risk but only about 1-4% of young people at low risk.