The fourth quarter of 2018 was horrible for Wall Street with the key indexes losing in double digits. A flattening yield curve causing recessionary fears in the United States led to this massacre. And why not? The return of global growth concerns pulled down long-term treasury yields meaningfully while a hawkish Fed kept pushing short-term rates higher.While six out of the 11 sectors in the S&P 500 have so far undergone double-digit losses, per an article published on Wall Street Journal, below we highlight a few key ETF areas that have lost around 30% so far in the quarter (as of Dec 19, 2018).EnergyConcerns over rising output amid softer-than-expected U.S. sanctions on Iran and falling demand from global growth worries have weighed on oil prices in the fourth quarter.United States Oil USO haslost about 35%in the quarter. Even the fresh output cut decided by the OPEC and Russia in early December for the first six months of 2019 could not save the liquid commodity (read: Is Fresh OPEC+ Output Cut Enough to Boost Oil & Energy ETFs?).SPDR S&P Oil & Gas Equipment & Services ETF XES (down 45.2%), Invesco S&P SmallCap Energy ETF PSCE (down 44.4%), VanEck Vectors Oil Services ETF OIH (down 41.4%) and Invesco Dynamic Oil & Gas Services ETF PXJ are of the worst-performing energy ETFs of the fourth quarter.MarijuanaMarijuana stocks and ETF were hot trades in 2018 due to growing efforts for legalization, both for medical and recreational usages, it saw a volatile phase in November on bubble fears and some downbeat earnings releases. ETFMG Alternative Harvest ETF MJ is down 35.5% so far this year (as of Dec 19, 2018) (read: What Went Wrong With the Marijuana ETF on Wednesday?)Some industry experts are of the view that overvaluation is a threat to the space. It does have bright long-term prospects. But things will probably shore up slower than anticipated. Probably this is why despite going through the roof in mid-September, the fund succumbed to a steep slowdown in December (read: Will Cannabis ETFs be on a High Again?).BiotechThis fund follows an index, which is equal weighted and is designed to measure the equity market performance of the common stock of U.S. exchange-listed biotechnology companies with a primary product offering that is in a phase 1, phase 2 or phase 3 clinical-trial stage of development.Being a high-beta and high-growth sector, biotech has been beaten down badly on a broad market rout. Some sector-specific news also played foul. The world's biggest maker of health care products Johnson & Johnson (JNJ) had a tumultuous ride in December on reports that its baby powder contained cancer-causing asbestos.Also, a federal judge in Texas ruled that President Barack Obama's signature health law — the Affordable Care Act (ACA) or Obamacare — is unconstitutional in December. Virtus LifeSci Biotech Clinical Trials ETF BBC is off 33.2% this quarter (read: Healthcare ETFs Sink on JNJ News, ACA Ruling: What???s Ahead?).Tech & MediaIt is one of the prominent spaces which saw huge selloffs in 2018. Investors should note that tech stocks, particularly FAANGs, were once investors’ darling this year. However, things took a turn, causing a steep slump in Wall Street, in the October-November period. Rising rate worries, overvaluation and U.S.-China trade tensions led to the upheaval (read: 5 Low P/E Tech ETFs for Investors).Per an article published on Associated Press, technology and Internet-based companies normally see high profit margins. In a rising rate environment, the profitability of such companies will be compromised as they will end up paying higher interests on borrowed money. As a result, AdvisorShares New Tech and Media ETF FNG is down 30.3% in the fourth quarter.Want key ETF info delivered straight to your inbox?Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report PWRSH-DYN OIL&G (PXJ): ETF Research Reports PWRSH-SP SC EGY (PSCE): ETF Research Reports SPDR-SP O&G EQP (XES): ETF Research Reports VANECK-OIL SVC (OIH): ETF Research Reports US-OIL FUND LP (USO): ETF Research Reports BIOSH-BIO CLNCL (BBC): ETF Research Reports ETFMG-ALT HRVST (MJ): ETF Research Reports ADVS-NW TEC MDA (FNG): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report