It 's the most widely used illegal drug in the world , but does cannabis deserve its reputation as being one of the safest ? Not if you take a look at South Africa , one of the UK 's biggest providers of high-strength cannabis , where a potent strain of the plant dubbed 'swazi gold ' is wrecking havoc on its young population . As revealed in BBC 's Stacey Dooley Investigates , which aired last night , poverty-stricken grandmothers are growing it , drug mules are risking their lives to smuggle it out of the country , and what stays behind is ruining the lives of South Africa 's drug-addled teens . Scroll down for video . Confiscated : Reporter Stacey Dooley ( left ) poses with blocks of densely-packed cannabis which have been intercepted by officials ( centre and right ) at South Africa's O R Tambo International Airport . Swazi gold is grown in the tiny South African sovereign state of Swaziland , where the climate and nutrient-rich soil is perfect for growing marijuana . Farmers - many of them 'Grannies ' whose children have died and who are now in charge of providing for their grandchildren - have developed the potent strain through cross-pollination , and can now yield double the crop they once could annually . The result is cannabis which boasts a staggeringly high concentration of THC , the psychoactive agent which produces the high , which finds its way either to the streets of the UK , or the streets of Johannesburg and beyond . 'We do n't care where it ends up , ' one farmer tells reporter Stacey Dooley . The swazi gold that stays in South Africa is now commonly mixed with heroin to make a highly addictive new cocktail known as nyope . Nyope contains a heroin concentration of around ten per cent , and often 'fillers ' including rat poison and crushed HIV tablets . Hooked : South African youths as young as 14 are mixing swazi gold with heroin to form nyope , a highly addictive substance that causes long-term mental problems ( file photo ) ' I smoke until I die , ' one young addict based in Johannesburg 's Ivory Park tells Ms Dooley . ' I get crazy if I do n't get this . ' 'We want to stop but if you are addicted you ca n't just leave , ' complains another . Nyope addicts , many starting out as young as 14 , smoke an average of 15 heroin-laced 'joints ' per day . They go through stages of painful withdrawal on a daily basis between bouts of being high , with symptoms including restlessness , aching bones and nausea ; and most are left with lifelong mental problems as a result of taking the drug . Ms Dooley meets one 18-year-old nyope addict called Tulu who attends a rehab centre every day in a bid to turn his life around . He has been clean for three days when Ms Dooley meets him , and says he 's determined to kick the habit . Lucrative : Farmers in Swaziland developed the potent strain through cross-pollination , and can now yield double the crop they once could annually ( file photo ) Tulu 's parents died when he was just 11 , leaving him alone to look after his younger sister . 'She 's eight , I have to give her something so she can eat at school , ' he explains . It 's difficult to know where to start when it comes to cracking down on South Africa 's drug trade , Ms Dooley concludes . Farmers and dealers simply pay off corrupt members of the police force to avoid being arrested on a daily basis , and the story is much the same in airports . When Ms Dooley visits Johannesburg 's O. R. Tambo International Airport , she witnesses one incident of a suitcase packed with cannabis being intercepted , but airport officials admit that more often than not , drugs get through . As for Tulu , when Ms Dooley goes back to his home town to check on him , he has stopped attending rehab . Nyope , it seems , has reclaimed another victim .
The strain is grown in Swaziland , one of South Africa 's poorest states . It has extremely high levels of THC . South African countries combine it with cannabis to produce potent drugs .