Very possible, in fact, at least in part. One of the most fascinating areas of psychiatric research is the interplay between T-lymphocyte function (thought to resist the growth of cancers) and depression. Dr. Marvin Stein at Mt. Sinai in the 70s and 80s, his protege Dr. Steven Schleiffer and others thereafter, demonstrated decreased T-lymphocyte function in depressives, with improved lymphocyte function when depression remitted. They demonstrated decreased survival in breast cancer patients who became depressed (carefully controlling for the stage of illness and level of debility, to insure that the more depressed subjects weren't depressed because they had more severe illness than the non-depressives.) Paterno looked very sullen the past few months, and this might have rendered his body less able to ward off the lung cancer.