Doubling your money isn't as difficult as it might seem. You just need the right stocks and enough time. I'm not talking about 50 years. There are plenty of stocks with the potential to at least double in five years or less.

Three stocks that I think could double your money in a relatively short time frame are Guardant Health (GH 3.67%), The Trade Desk (TTD 0.92%), and Vertex Pharmaceuticals (VRTX -0.69%). Here's why I'm especially optimistic about the prospects for these three stocks.

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1. Guardant Health

I don't own Guardant Health yet, but it's at the top of my list for buying next. The stock began trading in October 2018 and is already up more than 170%. My view is that there's still plenty of room to run for Guardant Health.

The company is a pioneer in developing liquid biopsies to detect cancer. You don't have to understand all of the complicated science behind Guardant Health's technology to know that there's a huge potential for its products. Currently, many types of cancer can't be detected until tumors have grown large enough to cause health issues. Liquid biopsy offers the ability to detect cancer at very early stages by finding tiny fragments of DNA that have broken away from tumors and sometimes fully intact tumor cells that have split off from the tumor.

Guardant Health already has two liquid biopsy products on the market. One helps physicians match cancer patients with the best treatment for the type of cancer that they have. Another helps drugmakers screen patients in clinical trials to make sure they're a good fit for specific therapies. The company estimates that the total market for its current liquid biopsies in the U.S. alone is close to $39 billion.

Even after its big run, Guardant Health's market cap stands at around $8.4 billion. Investors are clearly betting that the company will generate tremendous growth. I think that's a pretty good bet and think that this stock could double and perhaps a lot more over the next few years.

2. The Trade Desk

I was a little late to the party with The Trade Desk. But I bought shares earlier this year and haven't regretted it one bit. The stock has more than doubled so far in 2019 and is up over 700% in the last three years.

The Trade Desk bills its core product as "the future of advertising." That's not just spin, in my opinion. The company provides a platform that ad buyers use to purchase and manage digital advertising campaigns. In the past, buyers negotiated contracts for advertising in a process that could take weeks to wrap up. The Trade Desk enables immediate placements of targets ads across the entire spectrum of digital outlets, including social media platforms and websites.

Perhaps the greatest growth opportunity for The Trade Desk is connected TV (CTV) -- TV connected to the internet, like streaming services. Sure, some streaming services are subscription-only with no advertising. But with so many streaming services now available and on the way, it seems highly likely that companies will offer ad-supported versions to hold down costs for subscribers.

The Trade Desk sports a market cap of nearly $11 billion with the stock trading at around 68 times expected earnings. That might seem like such an inflated price that there's nowhere to go but down. But with Wall Street analysts projecting the company will grow its earnings by 29% annually, I think this high-flying stock could double investors' money relatively quickly.

3. Vertex Pharmaceuticals

My view is that Vertex Pharmaceuticals is the best biotech stock on the market right now. Although Vertex hasn't delivered awe-inspiring gains so far in 2019, the stock as more than doubled over the last three years. And I predict great things ahead for the company.

Vertex already claims a virtual monopoly in treating the underlying cause of genetic disease cystic fibrosis (CF). Its three approved CF drugs are currently used by less than half of the patients that could be treated by the therapies. Vertex thinks that it can pick up additional indications for younger patients to push its growth prospects up another 50% or so.

But Vertex will soon file for approval of a triple-drug combo for treating CF that could add a lot more to its addressable market. The biotech is also developing drugs to treat several other diseases outside of CF and recently acquired Exonics Therapeutics to expand even further into other rare genetic diseases.

Vertex's forward earnings multiple of 29 might look a little pricey. However, the company could easily grow earnings by 45% annually over the next five years. I think Vertex's chances of at least doubling investors' money during that period appear to be very good.

High growth, high volatility

There's one downside to these three stocks that investors should know about. All three definitely have the potential for high growth, but they also could experience high volatility. 

It's possible that Guardant Health, The Trade Desk, and Vertex will see big price swings both up and down over short periods. But I wouldn't worry if the stocks go down for a while. Give them a few years and I suspect you'll be happy you held on to what, in my opinion, are high-probability winners.