TRENTON, N.J. -

Veterans and others in New Jersey can now legally treat their post-traumatic stress disorder with marijuana.

Republican Gov. Chris Christie signed a measure Wednesday that allows people to use marijuana if their PTSD isn't treatable with conventional therapy.

But Christie also directed the state's health commissioner to promulgate additional regulations that provide "clear objective criteria" regarding the drug's use for PTSD.

Christie has said he wants to make sure legalizing medical marijuana doesn't become a backdoor into legalization for recreational use.

New Jersey is the 18th state to allow medical marijuana to be used to treat PTSD.

Marijuana is also approved in New Jersey to treat multiple sclerosis, terminal cancer and muscular dystrophy, among other medical diseases. It's also approved for seizures and glaucoma if those conditions resist conventional treatment.