Good age to diagnose personality disorders

Is age 18 too young to diagnose personality disorders? Although you are an adult at that age, you are a teenager still. I think the best age to diagnose personality disorders is at least 25 or 23 at the youngest.

If a person get's diagnosed personality disorder as soon a person turns 18 years old, can the symptoms of it be acute and be improved overtime with help?

Psychology should develop Young Adult Onset Conduct Disorders for adults under 23, just like the case of Brian Blackwell.

Personality disorders can be diagnosed at age 18, if the behavioral problem is severe.