While a mind-altering-substance consumption alleviates current level of depression, it facilitates future depression. Our analysis incorporates this trade off and shows that the stationary state of a consistently overly ambitious sophisticated substance user is improved by impatience, and that...

A no-arbitrage rule of consumption and a golden rule of capital accumulation are derived under the assumptions that the satisfaction from consumption is spoiled by environmental degradation caused by industrialisation but moderated by cleaning up and greening operations.