a friend of mine who smokes marijuana says that he read somewhere that smoking a cigarette increases the marijuana high by 11%. is this true? please cite your answers.
Sorry-- I can’t give you any cites so ignore this post if you wish.
I can only offer anecdotal evidence. When I lived in the Netherlands I would, on occaision smoke a Dutch joint. That is-- a cone-shaped joint containing pot and tobacco. From my experience, and from the statements of people I know who also have smoked a mixture of the two, I believe that smoking the two together causes a more intense high. Why would it? I don’t know. I speculate that the tobacco does something to the lungs and/or bloodstream that increase the absorbsion and/or effectiveness of the THC, but I have know idea. It is also possible that the nicotine buzz simply makes you think you are higher but you are not.
In any event, this only takes into account smoking the two together-- NOT being a regular cigarette smoker and then smoking pure pot.
Well, you know it must be true, if the guy said it increased the high by precise number like 11%! 
And just how do we quantify how high somebody is, then decide their high is increased by 11%? The ‘high’ is very subjective, the degree of impairment varies from individual to individual, and quantifying the level of THC in the blood to attempt to correlate it with degree of impairment is not a science being actively studied.
Some pot smokers swear by caffiene, as it keeps them more awake to appreciate the buzz more. Since nicotine is also a stimulant, I’d not be surprised if it kept some marijuana user more alert during his use.
But 11%? Sounds like stoner babble to me.
QtM, MD