The internal and external validity of sluggish cognitive tempo (SCT) relative to attention-deficit/hyperactivity disorder-inattention (ADHD-IN) was evaluated with Turkish children and adolescents. Parents completed the SCT, ADHD-IN, ADHD-hyperactivity/impulsivity (HI), oppositional defiant disorder (ODD), callous-unemotional (CU), anxiety, depression, social impairment, and academic impairment scales of the Child and Adolescent Behavior Inventory (CABI) on 1015 Turkish children and adolescents (56% girls; ages 6–15 years; Mage = 10.05, SDage = 2.32), including 762 recruited from the community and 253 recruited from outpatient psychiatric clinics. SCT symptoms demonstrated excellent internal validity with the ADHD-IN symptoms. SCT symptoms also showed invariance across boys and girls as well as across community and clinical samples. SCT showed stronger first-order and unique associations than ADHD-IN with anxiety and depression whereas ADHD-IN showed stronger first-order and unique associations than SCT with ADHD-HI, ODD, and academic impairment. SCT and ADHD-IN showed equal associations with CU behaviors and social impairment. The current study is the first to support the validity of CABI SCT scores with Turkish children and adolescents and also replicates the findings from similar studies with children from South Korea, Spain, and United States. These findings thus further strengthen the transcultural validity of CABI SCT scale scores.
