Beware the carbohydrates, Phenomenon. I used that diet when I was trying to lose weight. I was very successful but once a simple frozen yogurt (20g carb) had stopped my ketogenic state for almost 3 days. There are hidden carbohydrates in everything, from meat to whey, so anything additional can mess your diet up.
I'm not sure it does touch the serotonin at all - I think the anti-epileptic effects come from a down regulation in the firing rates of over excited brain areas - possibly because ketones can't sustain them - what, by theory, if we are lucky enough, could selectively fix areas in our brain that over-inhibit sensory filtering causing HPPD, even if we don't touch the serotonin system. Maybe I said trash but whatever, let's try it.
http://www.wellnesscare.com.au/ketogenic.html
Note: this site says 20% carbohydrates what's probably too much. Don't forget buying a ketone unire test.