I can only say that opiates also gave me a boost of energy as well. I remember the last time (before my 5 months clean this year) I was drug-free in 2010 for Jan-March and started back again on codeine. My normal dose before quitting was 3 30 mg tabs at a time 3 times a day and I only took 2 since it had been 3 months. I remember my heart racing once the drug took affect and a burst of energy. In fact, it scared me a bit and it took me about a month to need the 3 at a time again to achieve a similar effect. Of course, after being back on a few months, I just needed to dose to feel "normal". I also planned my dosing back then on my activities. Needed that dose to go to the grocery store, get up and go to work in the a.m., prepare a holiday meal, go visit family or friends, etc.
Every time I have quit in the past, I am lethargic. Just getting out the bed and putting on my clothes is a chore. I don't want to do all the things I just listed and my addict mind tell me I cannot get through any of it w/o the drug. It always takes a few weeks to a month to feel better. I can say that after 5 months this time, I do have my normal energy level back. Just took a week's vacation to New England this month and really enjoyed myself w/o drugs.
FT may have something here on the effect of opiates on some of us. I can also tell you that I have taken a few Xanax in my time and feel absolutely nothing and that drug is like no drug at all to me - does not make me sleepy and does not make me high. I read on SR everyday that some people have a serious problem with Xanax, expecially withdrawal. I think we are all wired differently and different drugs affect us all differently, but I am no expert . . just personal experience.