I have no idea about causal relationships but there is at least some data on opium production. According to the UN Office on Drugs and Crime, opium production

I have no idea about causal relationships but there is at least some data on opium production. According to the UN Office on Drugs and Crime, opium production jumped from 74,000 hectares in 2002 to 224,000 hectares in 2014, a ~200% increase. [0] (p. 12) Afghanistan is the world's largest producer of opium followed by Myanmar. > Opium poppy cultivation in Myanmar and Lao PDR rose to 63,800 hectares (ha) in 2014 compared to 61,200 ha in 2013, increasing for the eighth consecutive year and nearly tripling the amount harvested in 2006. [1] > In North America, although 90 per cent of the heroin in Canada originates in Afghanistan, the United States continues to be supplied by heroin manufactured in Central and South America. However, analysis of seizures indicates that while Afghan heroin currently accounts for relatively little of the heroin seized in the United States, this may be changing. [0]: https://www.unodc.org/documents/crop-monitoring/Afghanistan/Afghan-opium-survey-2014.pdf https://www.unodc.org/documents/crop-monitoring/Afghanistan/... [1]: http://www.unodc.org/unodc/en/frontpage/2014/December/opium-production-in-the-golden-triangle-continues-at-high-levels--threatening-regional-integration.html http://www.unodc.org/unodc/en/frontpage/2014/December/opium-... [2]: http://www.unodc.org/wdr2015/en/opiates.html http://www.unodc.org/wdr2015/en/opiates.html