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But what does this actually mean in practice?
In practice the hope is within ten years time there is a new diagnostic tool that uses actual research and points to functional, physiological, and genetic causes for mental disorders.

Making stuff up to illustrate...
So ADHD might become:
1) Genetically based reduction in core dopamine production with executive function impact(requires < .09ug...)
2) Prefrontal sensory overload (attention shutdown accompanied by increased xxx waves in yyy system)
3) Hyperglycemia accompanied by active burning of excess glucose

Where #2 might lead to ADHD like symptoms, it could also lead to exhibiting ASD like symptoms with pragmatic language issues and the inability to maintain eye contact or being overstimulated in crowds.

Under the current DSM approach, the #2 child chould be place on stimulants or placed in 12 months of pragmatic language training. Where what they really need is sensory management training.

The medical equivalent to the current DSM would be like:
Excess Mucus Disorder
Any 4 of these:
1) Runny nose
2) Watering eyes
3) Coughing
4) Sneezy
5) Doc
6) Bashful
7) Expectoration
Treatment: Tissue and chicken soup for 7 to 10 days.