I didn't read Dee's link as yet, but I believe there's a distinction between hangovers and withdrawals.
Hangovers occur when a person who is not accustomed to drinking overindulges on rare occasions. The body and brain are not used to the presence of alcohol and rebel against it.
Withdrawals occur only after dependence and tolerance to alcohol have been established through chronic heavy drinking. The brain and nervous system have become used to the presence of alcohol and rebel when it's taken away.
Some of the symptoms are indeed similar but the physiology is different.