I asked the question, Why would someone take methylfolate and not just OTC folate? I got an interesting response from Susan Whelan:
Hi, I work with Deplin. Maybe I can help? Deplin is l-methylfolate, the active form of folate, what your body makes naturally in the methylation process. L-methylfolate is the only form of folate that is capable of crossing the blood brain barrier to help regulate the neurotransmitters associated with mood. Folate occurs naturally in leafy green vegetables but is available as a supplement as folic acid. Approximately 70% of depressed patients have a genetic factor (called MTHFR) that limits their ability to convert folic acid to l-methylfolate. L-methylfolate is 7 times more bioavailable than folic acid. You read more about the difference here: http://www.deplin.com/DeplinFacts,VsFolicAcid
I hope this information helps.