never had a problem with weed,but I got drunk once and did about 4 lines and it took four or five days to recover,worst time of my life,but atleast I learned
Cogeners for one. These are byproducts of fermentation to which most people have some degree of alergic reaction. Also, due to the chemical nature of alcohol - and not its direct biotoxicity - drinking depletes vitamin and minerals as well as blood sugar. All are major contributory causes to an alcohol hangover.
"Hangover" in relation to drugs is, of course, most often used with regard to alcohol. However, the term simply referes to the undesired or unintended "after" effects of a drug.