Biotech exchange traded funds, market leaders for much of this year, stumbled in October as the government shutdown had an unexpectedly debilitating affect on the high-flying sub-industry.

The iShares Nasdaq Biotechnology ETF (NasdaqGS: IBB), which tracks large biotech or pharmaceutical companies listed on the NASDAQ, declined 3.3% in October. IBB is still up 51.1% year-to-date.

Biotechnology stocks have typically weathered the market storms, outperforming other areas during large macroeconomic problems. However, biotech ETFs plunged earlier in October at the height of the market volatility associated with the U.S. debt default scare. [Biotech ETFs Look to Claw Back After Shutdown Slump]

The shutdown slowed U.S. Food and Drug Administration’s normal drug approval cycle, a key driver of returns in biotechs.

Moreover, the slowdown in biotechs could be a sign that investors are concerned about valuations.