I've noticed, now that i've taken up cycling that i'm generally a lot happier and calmer in my daily life. Especially immediately after I bike I feel happy and sometimes almost euphoric, it's great. I know that this is a common side-effect of most physical activity because of the chemical releases triggered in your brain. But i'm wondering if there have been studies linking physical activity (and cycling specifically) with increased happiness etc... in daily life. I ask primarily because my sister I know is quite depressed and I want to get her interested in cycling with me and would like to be able to show her the proven benefits.