Coffee has no effect on me, or a paradoxal one (I am sleepy). My brother is the same. I wonder if there is some genetic component. I can go from 6 espresso a d

Coffee has no effect on me, or a paradoxal one (I am sleepy). My brother is the same. I wonder if there is some genetic component. I can go from 6 espresso a day to no coffee for a week, without any effects. This is fantastic because I like coffee a lot (except some days, and then I do not drink any).