This happened in 2013, after trying it a couple of times previously and thinking it made me feel worse, I decided to give it another shot. The first day I was surprised that I tolerated 2x400mcg. The next day I took 4x400mcg in the space of a couple of hours and suprisingly I had a the biggest lift in mood I have had in during CFS, it was the happiest I have ever been in 10 years. I ended up walking twice as long as I normally would, I was enjoying the music on my mp3 player a lot more, I felt really happy. It felt like my feel good chemicals were firing. After that though I never experienced anything like that again, despite trying many times by itself and with every co factor you could think of. I find it hard to believe it could just be placebo, considering my mindset was negative(thought that it made me feel worse in the past) I also find other B vitamins work randomly for me, some times good sometimes bad, but never to the degree of above.