Pakistan's already-rampant drug problem is likely to worsen after withdrawal of troops from neighboring Afghanistan—the world's leading producer of opium. The supply of opium and heroin (an opium derivative) into Pakistan has significantly increased over the past five years, according to analysts, prompting a swell in drug use and addiction. Estimates of the number of Pakistani drug users currently range from 600,000 to 9 million, according to the UN Office on Drugs and Crime, with the actual number probably somewhere in between. "[Drugs] are available like peanuts," says Dr. Saleem Azam, head of a rehab center in Karachi. "You are sitting in your office, you are sitting in your bedroom, you are sitting in your living room, you can call a person and he will drop the drug at your doorstep." The country's drug imports are expected to surge further when foreign combat troops withdraw from Afghanistan in 2014, loosening any control there currently is over opium production and smuggling in the region. According to the UN, the amount of Afghan farmland devoted to growing opium poppies has jumped by 20% over the last year.