Benjamin Graham, one of history's greatest investors, taught many investors -- including Warren Buffett, his student at Columbia University -- that the best way to find prospective investments was to search the papers weekly to find the market's most depressed stocks. So I've taken it a step further and searched for some of the most depressed stocks of this year in an attempt to try and figure out what went wrong and what the future holds for these market dogs.

Slashing dividends
First up is dividend slasher Atlantic Power (NYSE:AT), down 69% year to date.

What went wrong? Historically, Atlantic Power was a dividend company, paying out what seemed to be a secure annualized dividend yield of around 10% in monthly payouts. However, earlier this year the company slashed its payout from $0.10 per share per month to $0.03 per share per month. For many, this seemed like a prudent move, considering the company needed to conserve cash for expansion and debt repayments, but greedy dividend investors punished the company

But what does the future hold? It now seems Atlantic Power is in a better position than it was before. For example, Atlantic's dividend yield of 10.2% is now covered twice by earnings before interest, tax, depreciation, and, amortization -- a.k.a. EBITDA -- whereas before it was barely covered by EBITDA.

It's also important to remember that utility companies require a lot of capital equipment, which can lead to high depreciation costs. So, although a company may report a loss, it can actually be making a cash profit. This is exactly the case for Atlantic. Indeed, while the company reported a loss for the fiscal third quarter, it actually generated free cash flow of $38 million -- more than enough to cover the dividend payout.

What's more, the company is selling off noncore assets to reduce debt and reinvesting cash into renewable-energy assets, which should pay off over the long term. Green energy is supposed to be the next big thing, right? 

All in all, Atlantic's dividend appears to be safe for now, the company is committed to debt reduction, and investments in renewable-energy technologies should lead to long-term profits. Atlantic looks attractive at these levels -- did I mention the company also trades at a discount to book value?

Falling foul of the FDA
Next up we have Intuitive Surgical (NASDAQ:ISRG), which has lost about 22% this year.

Intuitive was originally sent sliding after the company revealed back in July that its da Vinci robot operating systems were under investigation by the FDA. It was also reported that the FDA was surveying surgeons about the safety of robot products.

What's more, the FDA reportedly found a number of deficiencies in Intuitive's incident reporting history. Things only got worse at the beginning of this month when the FDA revealed that the number of adverse incident reports involving Intuitive's robots had more than doubled this year. Granted, an increase in incidents naturally accompanies the increasing adoption of surgical robots.

But what now? More incident reports and increasing FDA scrutiny are hurting Intuitive's sales. In particular, the company reported that during its fiscal third quarter it only sold 101 da Vinci robot systems, compared with 155 a year earlier. Many analysts now believe that unless Intuitive comes up with some conclusive data on the benefits of the system, sales will continue to decline. However, there have been suggestions that Intuitive's problems are due to the fact that hospitals have been hesitant to spend large amounts of cash on the company's expensive robotic devices, as hospitals face many financial challenges.

Granted, Intuitive is buying back $1.5 billion of its own stock with the impressive cash balance it has built up during the past few years, which works out at about 10% of the company's market capitalization. Based on numbers reported for the fiscal third quarter, Intuitive has cash worth $31.60 per share.

Nonetheless, Intuitive continues to trade at a high earnings multiple, which, based on that fact that the company's sales are declining, looks to be unwarranted. Moreover, some might question the company's motives in using cash to buy back stock trading at a high earnings multiple.

Unless Intuitive can prove that its equipment is better than human surgeons, the company's sales will likely continue to decline. In addition, buying back stock at these levels does not look like good fiscal management. Maybe avoid this one for now.

A not-so-precious miner
Lastly, we have miner Coeur Mining (NYSE:CDE).

What went wrong? Coeur, like the rest of the mining industry, is suffering from contracting profit margins as costs rise and precious-metals prices fall.

But what now? Unfortunately, Coeur's fortunes are, for the most part, tied to the silver market and Federal Reserve policy. That said, the company's outlook is not all guesswork, as there are some signs that Coeur could be driving its own fortunes.

For example, between now and fiscal 2016, Coeur is targeting a compounded 25% increase in silver production, which should mitigate some declines in the silver price. In addition, according to fiscal second-quarter numbers, Coeur's net debt-to-equity ratio was less than 5%, which gives me confidence that the company will be able to ride out these tough times in the silver market.

Having said all of that, according to my research, Coeur's average all-in sustaining cash cost of production per ounce of silver is around $19.43 based on fiscal second-quarter numbers, which indicates that the company's profit margin per ounce of silver sold at current prices is only around $1. 

Still, Coeur is trading at a discount to book, and in my opinion, this always mitigates some risk when investing in companies with a mixed outlook like Coeur. Taking a longer-term view, I feel Coeur is destined for greatness. The company is preserving cash and ramping up production, and it should benefit from rising silver prices in the long term.

It takes time
So in the case of Coeur and Atlantic, it would appear that investors have punished the companies for short-term mistakes with no concern for their long-term outlooks. It's no secret that investors tend to be impatient with the market, but the best investment strategy is to buy shares in solid businesses and keep them for the long term. In the special free report, "3 Stocks That Will Help You Retire Rich," The Motley Fool shares investment ideas and strategies that could help you build wealth for years to come. Click here to grab your free copy today.