A lot of epidemiological research involves estimating the average risk of depression in groups of people characterized by different risk factors etc. A different challenge is to estimate or predict the risk in a specific person - a goal that is more difficult but in some ways more useful (for example, in supporting individual treatment decisions). Dr. Jian Li Wang at the University of Calgary has developed one of the first ever personal depression risk calculators. Anyone can use it. A brief description of the work and a link to the calculator may be found here.