And recent studies show that children with serious depression often receive significant long-term benefits in their lives from being treated with medicines.

CNN: What can cause depression in a 12-year-old?

Last week, Barclays Capital recommended an equal weight position on Petrobras, citing its prospects as a good long-term hold, but warned of short term depression in the stock.

FORBES: What Forbes Readers Think About Brazil's Petrobras

But that price depression usually represents the opportunity for long-term investors to bag higher returns from these neglected stocks than from the more exciting stocks, says Haugen.

FORBES: Fiscal Cliff Or Not, Low-Volatility Stocks Tend to Outscore The More Exciting, Highly Volatile Plays Over The Long Haul

Dr. Tator said researchers now recognize the relationship between repeated concussions and depression, a breakthrough on the way to understanding long-term neurological effects of concussions.

FORBES: Should you pledge your youth sports athlete's brain to science?

"This is probably the best in terms of long-term follow study that I've seen in terms of associating dementia with depression, " said Dr. Richard Isaacson, associate professor of neurology at the University of Miami's Miller School of Medicine, who was not involved with the research.

CNN: STORY HIGHLIGHTS

Because our economic future depends on a financial system that encourages sound investments, honest dealings, and long-term growth, we've proposed the most ambitious financial reforms since the Great Depression.

WHITEHOUSE: Job Creation and Economic Growth

In the short run, we had to add to that long-term debt figure in order to stimulate the economy and keep us from moving into a depression.

WHITEHOUSE: VP Biden on Economic Expansion for the Middle Class

Another lesson from the Depression is that spending on infrastructure helps, and can also be an excellent long-term investment.

WSJ: How Obama Can Fix the Economy

Low-birth weight is linked to an increased risk death and disability, and a range of long-term health problems, such as diabetes, heart disease, Attention Deficit Hyperactivity Disorder (ADHD) and depression.

BBC: NEWS | Health | More tiny babies being born in UK