Should also note that the return to baseline was only after discontinuation of the MPH. Can't really tell if it would return to baseline if the medication was continued without digging into the study more than I have so far.

Also worth noting for those less familiar with medication names, methylphenidate is sold under the brand names Ritalin and Concerta.

The authors show increased depression risk in the 90 days PRE-exposure (before starting treatment). To me, the authors seems to have dangerously misinterpreted the data. It could easily be the case that a depression diagnosis leads to seeing a psychiatrist and deciding to treat their underlying ADHD with methylphenidate. How could being about to go on methylphenidate in the next 90 days possible be the cause of depression???

You misread it. It went back to baseline after discontinuing the treatment which means that the increased depression was during the time while taking the medication.