Global sales of antidepressant drugs are expected to exceed $20 billion by 2030. Now, some investors are betting that psychedelic therapies can grab a share of that enormous market.

Due to their mind-bending qualities, substances like psilocybin, ketamine, LSD and MDMA remain illegal in most of the world.

That may help explain why markets are showing strong doubts about the industry. A CNBC examination of seven psychedelic stocks that trade in the United States found that most of them are close to their 52-week lows as of mid-February, with some more than 80% lower than their 52-week highs.

But venture firms that invest in the new industry are standing by the drugs.

"Psychedelic healthcare is a very exciting area because it's really this apex of drugs, clinics and experimental treatments," said Clara Burtenshaw, a partner at Neo Kuma Ventures, the largest European venture capital fund that invests in psychedelic companies such as Atai Life Sciences and Compass Pathways.

As interest from the medical community and investors grows, what's next for the psychedelic therapy market? Watch the video above to find out.