I know when I took it I was sometimes kindof on edge-not really what I would call emotional, just more easily agitated I guess.
Phentermine stimulates neurons in the brain to release neurotransmitters that signal that "fight or flight" response in the body. You know that feeling you get when you're uneasy about something, like you're walking to your car alone in a dark parking lot? Or walking through the woods and hear a noise behind you? THAT's "fight or flight". It's our bodies way of protecting/preparing ourselves for danger. No way we can think about twinkies when that's going on, lol. Don't get me wrong-it's not like phen will make you feel scared-I'm just using those scenarios as an example of how our bodies produce those neurotransmitters naturally. It just makes the brain make those same chemicals.
It's a weird way to go about it, but when our brains/bodies are in this mode, the hunger signal can't get through-which is how phen supresses our appetite. So because it goes through the brain to alter mood to block hunger, I'm sure it can have different effects on different people. It's also one of the reasons why some people can't tolerate taking it, why it can cause insomnia, and why you can't take it if you are or have been taking maoi inhibitors (anti-depressants).