Both smokers and heroin addicts have significant levels of beta-carbolines in their systems. https://www.sciencedirect.com/science/article/abs/pii/S0006291X040

Both smokers and heroin addicts have significant levels of beta-carbolines in their systems. https://www.sciencedirect.com/science/article/abs/pii/S0006291X04025999 https://www.sciencedirect.com/science/article/abs/pii/S00062... https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1530-0277.1996.tb01034.x https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1530-0277.... (paywall, sorry)