'Pot stock' GW Pharmaceutical is flying high this year

The broader U.S. stock market has only seen slight gains this year, but shares of GW Pharmaceuticals are flying high in 2016.

The pharmaceutical company known for its cannabis-based drug trials to treat children's epilepsy has seen its shares rise nearly 20 percent this year, while the benchmark S&P 500 index is up just 2 percent.

GW's stock has also spiked 43 percent over the past six months.

GW 2016 performance

The stock closed up nearly 4.5 percent Wednesday.