Westermeyer J
Am J Epidemiol. 1979 May;109(5):550-62. doi: 10.1093/oxfordjournals.aje.a112713.
Crude rates of opium addiction were determined in 1972-1974 in ten communities of Laos, representing eight different ethnic groups and three provinces. In six rural communities, data were obtained by a house-to-house survey, and in four urban communities by opium den registration. Communities raising opium poppy as a cash crop had highest crude rates of addiction (7.0-9.8 addicts per 100 people). Thos involved in opium commerce had intermediate rates (4.1-5.5). Where neither opium production nor commerce was present, the communities had the lowest rates of addiction (1.8-2.3).