No, we did not combine any substances except for maijuana...but headaches tended to occur with and without it, hence that's not the matter..
We always eat shrooms on an empty stomach... Maybe dehydration could be the reason!. Talking about brain over-stimulation...can't agree here, as acid has never caused any headaches, even in large doses, nearing 500 mcg. The thing is, there are three main active components in shrooms: psilocybin, psilocin and baeocystin (not sure about spelling here), and amount of all three can vary. It could be that large doses of baeocystin, for example, caused the headache. Not really sure. Also, apart from the psychoactive ingredients mentioned above, the shrooms, being an organic substance, must contain a wide variety of other chemicals, which could turn into [relatively] toxic substances during the metabolism. Moreover, the action of shrooms depends on the conditions they were cultivated in...There are just too many factors that could contribute to the headache, unfortunately. However, any info on this subject would be appreciated :)