Uncertainty is rarely healthy for investors' portfolios. The fear that accompanies that uncertainty usually weighs on stock prices until it's dispelled by greater clarity.

For health care investors, with the exception of a few biotech stocks with upcoming binary events -- drug approvals and the like -- there may be no greater unknown today than the final shape of health-care reform legislation.

Many companies will eventually be affected by health care reform, but health insurers seem to be taking the brunt of the pain. These usually staid stocks have turned into roller coasters along the lines of Citigroup (NYSE:C) and American International Group (NYSE:AIG), whipsawing at the whim of politicians' latest words. Look at what some of these companies have done so far this year:

Company

Low price in 2009

High price in 2009

Gap Between Low and High

UnitedHealth Group (NYSE:UNH)

$16.18

$ 30.25

87%

WellPoint (NYSE:WLP)

$29.32

$55.73

90%

Aetna (NYSE:AET)

$18.66

$34.87

87%

Cigna (NYSE:CI)

$12.68

$30.63

142%

Humana (NYSE:HUM)

$18.57

$46.01

148%

Source: Yahoo! Finance.

Okay, maybe those swings aren't as big as Citigroup's 682% low-to-high gap this year, but they're certainly a lot bigger than the S&P 500's 56% gap.

The extreme highs and lows for these companies are likely only to continue until Washington has made up its mind on what the healthcare reform bill will look like.

When will that happen? That's what we'd all like to know. Take our poll and let us know what you think of health reform in the comment box below.

UnitedHealth Group is a Motley Fool Stock Advisor recommendation. UnitedHealth and WellPoint are Inside Value recommendations and the Fool owns shares of UnitedHealth.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.