Call it "The Murphy Effect."

Since Gov. Phil Murphy was sworn in on Jan. 16, a total of 4,200 patients have registered with New Jersey's medicinal marijuana program, according to an announcement Tuesday by state Health Commissioner Dr. Shereef Elnahal.

New Jersey has now reached a new milestone: 20,000 people enrolled.

That figure includes 1,500 who enrolled in the last month, when the pro-cannabis governor expanded the qualifying medical condition list to include chronic pain and anxiety.

"We're adding 100 new patients every day," the commissioner said. "This demonstrates that there was pent-up demand. People with chronic pain now have the option of medicinal marijuana instead of opioids, and more than 100 strains are available."

Expect those numbers to continue climbing rapidly, as the Murphy administration launches a $50,000 media campaign to promote the program.

Besides adding new qualifying illnesses, Murphy changed the program in March by cutting registration and renewal fees from $200 to $100 every two years, with senior citizens 65 and older and veterans added to the category of patients who pay only $20.

Doctors who want to participate in the program are permitted to keep their name off the online list of physicians, a change that recognizes some are not ready to shake the stigma of recommending cannabis as a medicine.

Approximately 600 physicians are now participating in the program, including 50 physicians who joined in the last month, Elnahal's announcement said.

Patients in New Jersey are served by five dispensaries, located in Montclair, Bellmawr, Egg Harbor, Woodbridge and Cranbury. A sixth is expected later in the spring in Secaucus.

Patients have expressed concern the dispensaries won't be prepared to meet the growing demand, as many ran out of strains before Murphy took office. The health department is reviewing applications from the five dispensaries owners to expand the number of retail and growing locations. The department has not yet disclosed those additional locations.

Additional information about medical marijuana in New Jersey may be found at

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Susan K. Livio may be reached at slivio@njadvancemedia.com. Follow her on Twitter @SusanKLivio. Find NJ.com Politics on Facebook.