When people discuss methamphetamine addiction or fairly chronic use over a long period of time, the understandable focus is the effect of the drug on the brain and ones mental health etc. However, I think people overlook the impact that excessive stimulant use (too much, too often and with insufficient recovery time) has on the body's hormones and physiological processes, processes which I don't believe are as resilient as the brain.
What Me_2 said above about his body needing the drug is related to an area I have been looking into recently.
If you are using meth then your adrenals are working overtime and your cortisol levels are extremely elevated, something which the body is used to doing in other situations but not for a long period of time. Basically, with frequent use your adrenals burn out. The well researched consequences of chronically elevated cortisol levels accords with some of the negative consequences I have experienced from frequent use. If you get to this point then once use of the drug ceases, adrenal fatigue sets in and wreaks havoc on your life. People might put this down to the impact of the drug on mental health, your emotions and simply because you are "overtired" from insufficient sleep, which of course is relevant, but the impact on your hormones and physiological processes underscores this and makes it seem so much worse. It goes way beyond simply not getting enough sleep or nutrition.
If anyone is interested then have a read of this article -
http://www.drlam.com/articles/adrenal_fatigue.asp.
If you are or have been a heavy user of meth over a long period of time, or even in the short term after binges, I have no doubt that reading this article will be like holding up a mirror to yourself, with every symptom or consequence described being experienced at some stage and likely most of them at once.