Administer the CBCL to quantify externalizing behavior severity and use the subscale profile to guide the diagnostic formulation.

The CBCL quantifies behavioral severity but does not assess the underlying etiology or comorbidities that drive the behavior. A severity score alone cannot clarify what is causing the antisocial behavior.

Assess for trauma history, ADHD, substance use, mood disorders, and the family/environmental context driving the behavior.

Antisocial behavior in adolescents is a final common pathway for multiple conditions. ADHD impulsivity can manifest as rule-breaking, trauma can present as aggression and emotional numbing, substance use drives theft and lying, and bipolar mania can cause impulsive antisocial behavior. Conduct disorder may still be the appropriate diagnosis, but the underlying contributors determine treatment. The callous-unemotional specifier (limited prosocial emotions) has prognostic implications. The family and environmental context (parental substance use, domestic violence, poverty, gang involvement) significantly influences both the presentation and the treatment approach.

Diagnose conduct disorder now, since the 18-month pattern of aggression, deceit, and rule violations clearly satisfies DSM-5 diagnostic criteria.

Diagnosing conduct disorder without assessing comorbidities misses treatable underlying conditions. The behavioral pattern may meet criteria, but the underlying contributors must be identified to guide treatment.

Diagnose antisocial personality disorder given the persistent lack of remorse and the escalating pattern of violating the rights of others.

Antisocial personality disorder cannot be diagnosed before age 18. In adolescents, conduct disorder is the appropriate diagnostic consideration.