At any age, diagnosis is based first and foremost on problems disrupting a person's life. This is judged by behaviour that is *demonstrably* different from that of the person's peers. Obviously that's trickier with small kids, but not impossible. Recently I asked my mother about my childhood "energy level" without mentioning that I suspect I have ADHD, and she was suddenly rattling off distinct and vivid examples of how different I was from other kids.

I wish I had been diagnosed at a young age and not gone through a lifetime of failure to thrive, suffering with the knowledge that I'm not accomplishing anything at all let alone living up to my potential, and blaming myself and others. Sure I've had traumatic childhood experiences; a narcissistic parent and an avoidant one, but I'm more resilient than for poor (but largely well-intended) parenting to have affected me in such a pervasive way.

A lot of anguish and blame could have been avoided if we didn't stigmatize or try to erase REAL mental illnesses or pretend they can never happen to kids. By all means withhold the meds till they get older (and have schools accommodate this), but I think it's wrong to pretend kids can't be mentally ill or that because diagnosis is more difficult, it's somehow wrong to try at all.