initiation. Moreover, an extended version of the CCC model that includes ‘upstream’ environmental risk factors has shown that risk of cannabis initiation and subsequent progression to cannabis abuse can be explained, in part, by environmental factors influencing cannabis availability28. One study examined CCC models across different classes of psychoactive substances29. The association between risk factors for initiation and risk factors for abuse or dependence was strongest for cannabis, intermediate for cocaine and weakest for sedatives and non-cocaine stimulants.
