 - History of regular alcohol consumption within 6 months of the study defined as: an average weekly intake of greater than 21 units or an average daily intake of greater than 3 units males, or defined as an average weekly intake of greater than 14 units or an average daily intake of greater than 2 units females. One unit is equivalent to a half-pint 220mL of beer or 1 25ml measure of spirits or 1 glass 125ml of wine. 