Alcohol is a dangerous substance that is toxic to the brain. It can cause permanent brain damage when taken in excess, leading to a decline in mental function. It is also a leading cause of death in the Western world. In 2010, there were nearly 9000 alcohol-related deaths in the UK alone, and that outnumbers the deaths caused by all illegal drugs combined.
ONS. 2012. Alcohol-related Deaths in the UK, 2010.
Taffe MA et al. Long-lasting reduction in hippocampal neurogenesis by alcohol consumption in adolescent nonhuman primates.