Most studies in neurology have too few test subjects to be scientifically sure. Those insufficient size studies are the basis for all domain-specific diagnoses in neuropsychiatry, since the few large enough studies there are always find individuals with the brain changes thought to be associated with a mental condition but without any of the symptoms. The only diagnoses that can be validated through large enough brain studies are those on serious brain damages and neurodegenerative diseases that destroy most of the brain.
Neuroscience 