"Subclinical cases" is pretty much just an euphemism for anecdotal evidence. I have experienced anxiety as well as mild depressive episodes when I was on methylphenidate. From my experience, those were just indications that I was not responding well to methylphenidate. After I switched to dextroamphetamine, I have not experienced any mood related side effects at all. No offence, I think it's a false association to claim that ADHD medication can unveil mood disorders.