If it does, how does this cross-drug adaptation occur? It is not as simple as variation in smoking topography with multiple studies failing to find any differences in inhalation patterns, lung capacity measured by breath holding, puff volume, or other characteristics (66-69) of inhaled drug use between cannabis smokers with those who smoke both cannabis and cigarettes. Smoking may serve as a cue - persistent exposure to smoking cues along with the associated pharmacological effects may well be learned, conditioned cues that can trigger use or relapse (70). There is also the possibility that cigarette smokers experience more positive subjective reactions to cannabis smoking and therefore, continue to use it. Distinct from aero-respiratory adaptation, these experiences reflect drug sensitivity, including experiences such as dizziness, giggling, a pleasurable rush or buzz and nausea (71-73), although coughing is also included. This effect may be environmental – one twin study noted that the extent to which the same genetic factors influenced subjective reactions to tobacco and cannabis was modest (74). In addition, implicit cognitive processes (i.e. an expectancy that cannabis smoking is less
