A study conducted by researchers at University College London has found that moderate alcohol consumption increases cognitive function. From the abstract:
Of people who reported drinking alcohol in the past year, those who consumed at least one drink in the past week, compared with those who did not, were significantly less likely to have poor cognitive function. The beneficial effect extended to those drinking more than 240 g per week (approximately 30 drinks).
The authors concluded that for middle-aged subjects, increasing levels of alcohol consumption were associated with better function regarding some aspects of cognition. Nonetheless, it is not proposed that these findings be used to encourage increased alcohol consumption.