The Goodman Assessment Tool (Strengths and Difficulties Questionnaire)
The Goodman assessment tool, formally known as the Strengths and Difficulties Questionnaire (SDQ), is a brief screening instrument designed to measure psychological adjustment and detect psychosocial problems in children and adolescents aged 3-16 years (though validated up to age 25). 1
What the SDQ Assesses
The SDQ evaluates five distinct dimensions of child and adolescent mental health:
- Emotional problems (symptoms of depression and anxiety) 1
- Conduct problems (behavioral difficulties and rule-breaking) 1
- Hyperactivity/inattention problems (ADHD-related symptoms) 1
- Peer relationship problems (social difficulties with other children) 1
- Prosocial behavior (positive social behaviors and strengths) 1
The first four subscales combine to create a Total Difficulties Score, which serves as the primary screening metric for overall psychopathology 2
Psychometric Properties and Validity
The SDQ demonstrates satisfactory reliability and validity across multiple age groups and informants, with the Total Difficulties Score being more reliable than individual subscales. 2
Reliability Metrics:
- Internal consistency (Cronbach's alpha) averages 0.73 across subscales, with the Total Difficulties Score reaching 0.77-0.81 2, 1
- Test-retest stability after 4-6 months averages 0.62 1
- Cross-informant correlation (parent-teacher agreement) averages 0.34, with ICCs ranging from 0.21-0.44 2, 1
Validity for Detecting Disorders:
- SDQ scores above the 90th percentile predict substantially elevated probability of DSM-IV psychiatric disorders, with odds ratios of 15.7 for parent scales, 15.2 for teacher scales, and 6.2 for youth self-reports 1
- The emotional subscale shows moderate accuracy for Major Depressive Disorder (AUC = 0.67-0.85) and high accuracy for Generalized Anxiety Disorder (AUC = 0.80-0.93) 3
- The SDQ predicts behavioral disorders better than mood disorders 4
Administration and Informants
The SDQ can be completed by three different informants:
- Parents/caregivers (most commonly used, available for ages 3-16+) 1
- Teachers (provides school-based perspective) 2, 1
- Youth self-report (for ages 11-25 years) 5, 1
Parent and teacher versions demonstrate better reliability than youth self-reports, particularly for externalizing behaviors like hyperactivity 2
Age Range and Developmental Considerations
The SDQ has been validated across a wide developmental span from ages 5-6 years through age 25, though originally designed for ages 3-16 5, 2, 3
- The five-factor structure remains stable across pre-adolescence (10-12 years), early adolescence (13-15 years), and late adolescence (16-19 years) 5
- Factor loadings differ across age groups, with some items (particularly item 11 on friendship) showing weaker performance 5
- The instrument performs consistently across sex, race/ethnicity, and socioeconomic subgroups 4
Clinical Application and Screening Cutoffs
For screening purposes in general populations, use the Total Difficulties Score rather than individual subscales, as several subscales have reliability below 0.70 2
Cutoff Considerations:
- The traditional 90th percentile cutoff provides 39% sensitivity and 93% specificity 4
- Lowering the cutoff to the 80th percentile increases sensitivity to 63% while maintaining 87% specificity, which may be preferable for screening applications where missing cases has greater consequences 4
Important Caveats
- The Prosocial Behavior subscale shows unclear construct validity and conceptual clarity, so interpret this subscale with caution 5
- Interrater agreement between parents and teachers is modest (as expected for behavioral assessments), with correlations higher for males than females 2
- Self-reports discriminate better for emotional and peer problems, while parent/proxy reports discriminate better for hyperactivity symptoms 5
- Some subscales require correlated error terms in factor analysis for optimal model fit, suggesting item-level complexity 5