NEW YORK – If JPMorgan Chase can’t do well, investors worry that other banks may do even worse.

The New York bank, widely considered the strongest in the industry, reported a 4 percent drop in income last quarter Thursday on weakness in investment banking and more costs related to litigation over mortgage investments.

That bodes poorly for the other big banks — Citigroup Inc., Bank of America Corp., Goldman Sachs Group Inc. and Morgan Stanley — that are due to report results next week.

JPMorgan warned that continued uncertainty in global markets could hurt fourth quarter results, too. Its stock slumped, dragging down other large banks with it.

The New York bank’s third quarter net income dropped 4 percent to $4.26 billion, or $1.02 per share, on revenue of $24.37 billion.

The declines in investment banking results were caused by extreme volatility in stock and bond markets in the third quarter. Markets started to swing wildly in August after the U.S. government’s credit rating was downgraded and worries emerged that a default by Greece could hobble the European banking system. Investors have also worried that the United States might slip into another recession.

The huge swings led to a slowdown in debt issuance and a record backlog in IPOs, both sources of banking fees, as companies elected to wait out the turmoil and investors pulled money out of stocks and bonds.

JPMorgan Chase & Co.’s fees from investment banking fell 31 percent to $1 billion in the quarter. Debt underwriting fees fell 37 percent to $496 million as fewer companies raised money by selling debt. With many IPOs also shelved, stock underwriting fees fell 47 percent.

JPMorgan’s stock fell 4.8 percent to close at $31.60 Thursday. Bank of America’s declined 5.5 percent to $6.22, Citigroup’s was off 5.3 percent to $27.64, Morgan Stanley lost 4.4 percent to $15.14 and Goldman Sachs fell 3 percent to $96.15.