Conduct disorder is only diagnosed in adults if they do not qualify for the diagnosis of antisocial personality disorder (spoiler: being diagnosed with personality disorder NOS [the most common personality disorder diagnosis, at least, under DSM IV-TR] with antisocial traits, among others, does not count as “antisocial personality disorder” and such an adult can still be diagnosed with conduct disorder). Otherwise, you will be dealing with adolescents and children when you refer to “conduct disorder”.

The difference between a kid with conduct disorder and one who is “a bad kid” is a matter of severity, pervasiveness, and duration. Such as it is with any diagnosable illness. When it is traits? When is it a disorder? Those are the points where the difference is made known.

The thing is, most cases of juvenile conduct disorder remit. They don’t grow up to be “bad people”.