'Headache' is kind of a vague term; wouldn't surprise me if 'anxiety' or others subsumed it.
That would be very strange. I don't believe it.
Here's what I think: the study was of people with ongoing post-concussion headaches. Therefore it made no sense to ask if they were getting headaches as a side effect. The 5g/day piracatem group reported a significantly larger improvement (decrease) in headaches than the placebo group.
Many people on LW have expressed interest in nootropics and cognitive enhancement. However, since people are presumably interested in the long-term efficacy, side effects and withdrawal symptoms of using various supplements, open-threads (which quickly become hard to navigate and only last a couple weeks anyway) are a sub-optimal place to discuss the topic.
So I thought I would create a permanent area for people who want to discuss the topic long-term.
Here are some "quick links" courtesy of gwern:
And Wikipedia's main page on the topic.