Vodka consumed in sufficient amounts, as any alcoholic beverage, can cause dehydration, digestive irritation and other symptoms associated with a hangover because these are inherent properties of ethanol, even if to a lesser degree than the methanol, fusel oils, and other alcohols which are absent in pure vodka.
Some scholars believe distilled spirits first starting being produced between the 8th century AD and 9th century AD in the Middle East. A popular legend is that St. Patrick himself introduced distillation to the British Isles, however it is likely he lived around the 5th century AD.