The Nasdaq's double-digit slide has investors spooked, and a look at past market peaks suggests the pain may not be over, even though stocks remain in a longer-term uptrend.

• Markets have erased over $2.5 trillion in value and nobody agrees on why, which itself is a warning sign.
• A historical pattern shows huge 18-year bull runs (like today's) are usually followed by a "lost decade" of flat or falling markets, as happened after 1929, 1968, and 2000.
• Investor borrowing to buy stocks is now near levels last seen before the 1929 crash, meaning any downturn could get amplified by forced selling.
• The Fed has started raising rates again, but overall money conditions are still loose, suggesting this is a rough patch rather than the start of a full-blown crash.
• Money looks set to rotate out of stocks and into gold in the coming months as the bumpy period continues.

Outlook: Expect continued choppiness in stocks for a while longer, with gold likely to benefit as investors look for safer ground before any durable market recovery.