U.S. stocks plunged today, closing down 390 points, or 3.5 percent, after hitting their lowest point this year. At one point the Dow was down more than 5 percent. European and Asian indexes closed down nearly 5 percent, driven by slowing growth forecasts from China and continued worries over Europe’s banks. Global commodities markets also fell, including gold. Analysts speculate that investors are likely reacting to the Fed’s acknowledgment that there are “significant downside risks” for the economy, as well as to fears over Greece and the apparent slowing of China’s growth.