So on Friday, I was smoking on some amazing girl scout cookies out of a pipe with some friends. We didn't have a grinder so we used our hands and we removed stems and so on because they said we'll get headaches. But I'm pretty sure we've smoked small stems before. But I decided to smoke a huge stem and see how it went down. So I took a hit and nothing like a harsh taste or anything abnormal. But after a while I got a throbbing headache and I was wondering, why do I get headaches off of a large stem and not small stems? And why do people get headaches off of them either way if they just have THC? Could it be something in the stem?