My question is just for curiosities sake as I do not wish to inquire with my colleagues. I am a Theoretical Physicist and my focus has always been the Cosmos and not the human brain. I never miss work and those around remain ignorant to the fact I am intoxicated. I refer to myself a functional drug user. I enjoy all drugs.. Hydrocodone, Oxycodone, MDMA, Methamphetamine, Cocaine..etc etc. I have found they allow me to explore theoretical concepts I would have ignored before. Regardless of which drugs I use, regardless of the dose or frequency, I have no problem quitting them cold turkey for an extended time. I also seem to have a higher tolerance than usual, even if I have never used the drug before. Any side effects of quitting are a minor irritation at best and never any serious withdrawals. That is with the exception of Marijuana, the drug that isn't supposed to form physical addiction. I get irritated and nervous if I think I am going to run out. I experience nausea and loss of appetite if I haven't smoked and the side effects remain until I smoke again. I assume it is genetic and has to do with the "wiring" in my brain and how my addiction centers function, however a medical opinion would be appreciated.