Findings from a US-based study released in September 2011 reveal that alcohol consumption raises the risk of making and repeating mistakes, due to a reduction in the brain's alarm response, causing the person to lose concern for the consequences of their actions, even ones that could result in harm to themselves or others.

http://www.sciencedaily.com/releases/2011/09/110901135030.htm
http://www.eurekalert.org/pub_releases/2011-09/uom-adb090111.php