Investors are losing faith in the economy's ability to withstand a possible recession, and that has taken a bite out of the stock market over the past couple of days. After seeing share prices fall sharply on Thursday, the Nasdaq Composite (NASDAQINDEX: ^IXIC) was down again in midday trading Friday, falling about 1%.

Investors often deal with situations in which news lifts an entire industry higher or lower. Yet it's important to remember that companies are often in direct competition with each other, and what's good news for one can be bad news for others. That fact was particularly clear among healthcare stocks  Guardant Health (NASDAQ: GH) and Exact Sciences (NASDAQ: EXAS) on Friday, as the two Nasdaq stocks moved in different directions after a key report.

Shares of Guardant Health had plunged 30% around midday on Friday. The move lower came after the company announced study results for its testing product for colorectal cancer, and even though Guardant seemed to view the outcome as favorable, shareholders didn't agree.

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Source Fool.com