The scary thing is, often the diagnosis is unclear yet still empirically treated. Good for the drug companies I guess:

The confusion is due in part to the patchwork nature of the health care system, experts say. Child psychiatrists are in desperately short supply, and family doctors, pediatricians, psychologists and social workers, each with their own biases, routinely hand out diagnoses.

But there are also deep uncertainties in the field itself. Psychiatrists have no blood tests or brain scans to diagnose mental disorders. They have to make judgments, based on interviews and checklists of symptoms. And unlike most adults, young children are often unable or unwilling to talk about their symptoms, leaving doctors to rely on observation and information from parents and teachers.