Here's a helpful hint for you: Ignore the market volatility. If you watch your stocks continually, the up-and-down swings could make you a nervous wreck. Invest with a long-term perspective, and the temporary market gyrations will be much less bothersome.

The good news is that there are plenty of stocks that provide opportunities to deliver excellent long-term returns. Here are three stocks that could even double your money within the next few years.

Person pointing to lighted dollar signs.

Image source: Getty Images.

1. CRISPR Therapeutics

CRISPR Therapeutics (CRSP 3.08%) isn't too far away from doubling this year, with its shares up close to 80%. But the biotech stock should still have plenty of room to run.

You'll want to especially watch CRISPR Therapeutics' lead pipeline candidate, CTX001. CRISPR and its big partner Vertex Pharmaceuticals are currently evaluating the gene-editing therapy in early stage clinical studies targeting rare blood diseases beta-thalassemia and sickle cell disease. The companies have already reported encouraging preliminary results from these studies and expect to announce additional data in the next few months. CTX001 holds the potential to essentially cure these diseases.

CRISPR Therapeutics also has a big opportunity with its three allogeneic chimeric antigen receptor T-cell (CAR-T) therapies in early stage clinical testing. Allogeneic CAR-T therapies use immune cells called T-cells from healthy individuals that are genetically engineered to target specific types of cancer then infused into sick patients. Current CAR-T therapies on the market use the sick patients' own T-cells -- an approach that's a lot slower and costlier than allogeneic therapies should be. CRISPR expects to report results from its early stage trial of one its CAR-T therapies, CTX110, by the end of this year. 

Sure, there's a real risk that CRISPR Therapeutics' gene-editing programs will flop. But so far, investors have plenty of reasons to be cautiously optimistic. If CTX001 or any of the company's allogeneic CAR-T therapies succeed in clinical testing, CRISPR Therapeutics should easily double in the not-too-distant future.

2. Fastly

Fastly (FSLY -1.29%) has taken investors on a really wild ride so far in 2020. The tech stock has had seven swings of at least 20% in just the last three months. But even with the turbulence, Fastly is still up more than 350% year to date.

The company's name hints at its underlying business. Fastly focuses on speeding up the delivery of apps and data over the internet through content delivery networks (CDNs) and edge computing. CDNs reduce the physical distance between servers and end users with a widespread distributed platform of servers. Edge computing takes a somewhat similar approach by moving app and data processing close to the cloud's edge -- the point where corporate networks connect with the cloud.

Fastly's addressable market currently totals more than $35 billion. It could grow much bigger than that with the unstoppable migration of apps to the cloud. Fastly has less than 1% of this market right now, giving the company a massive growth opportunity.

The company's biggest customer is TikTok, the video-sharing social network that has been at the center of a political firestorm recently. Until a deal is completely finalized to separate TikTok from its China-based owner ByteDance, Fastly's shares could remain highly volatile. However, Fastly's long-term prospects look great. 

3. Innovative Industrial Properties

If you have any doubts about how hot the U.S. cannabis market is, just look at Innovative Industrial Properties (IIPR 2.83%). IIP's shares have soared more than 60% so far this year and have skyrocketed close to 600% over the last three years.

IIP ranks as the leading real estate investment trust (REIT) focused on the medical cannabis industry. It buys properties from medical cannabis operators, then turns around and leases the properties back to the operators. This helps tenants raise cash while giving IIP a steady revenue stream.

The way for IIP to double is pretty simple: Keep doing what it has been doing. IIP currently owns 63 medical cannabis properties in 16 states, up from 46 properties in 14 states at the end of 2019. The company's attractive dividend, which currently yields nearly 3.8%, makes it even easier for IIP to deliver tremendous returns for investors.

It's possible that the legalization of marijuana at the federal level in the U.S. could pave the way for more rivals to enter IIP's market. However, marijuana legalization isn't a slam dunk by any means. And even if IIP faces increased competition in the future, the growth in the overall U.S. cannabis market should enable this stock to continue its winning ways.