Everyone is different. I'm in my 40s and throughout my while life have found that caffeine only has two effects on me: 1) If I have any later than afternoon, I

Everyone is different. I'm in my 40s and throughout my while life have found that caffeine only has two effects on me: 1) If I have any later than afternoon, I can't fall asleep when I want to, 2) If I have too much at once (like a single diet pop), I get the jitters. Otherwise, literally no effect. I sometimes drink tea in the morning for breakfast (a London fog) and it doesn't affect my cognition or mood at all.