Here is my contribution to not make you (or all others reading this) depressed RDS. First of all the calculations are wrong. From 78 years it does not drops to 49 because you sleep half the time! You sleep the third of the time approximately by average (i.e., 8 hours of 24 hours a day in every year). So that leaves with the added 26 not calculated years for you to live your life fullest!
Secondly neurology scientists have found why antidepressants work. It is by blocking the sFRP3 gene that releases depression related proteins.
References:
Jang, M. H., Bonaguidi, M. A., Kitabatake, M., Sun, J., Song, J., ... Song, H. (2013). Secreted frizzled-related protein 3 regulates activity-dependent adult hippocampal neurogenesis. Cell Stem Cell, 12 (2), DOI: 10.1016/j.stem.2012.11.021
Jang, M. H., Kitabatake. M., Kang, E., Jun, H., Pletnikov, M. V., Binder, ... Ming, G. I. (2012). Secreted frizzled-related protein 3 (sFRP3) regulates antidepressant responses in mice and humans. Molecular Psychiatry, 2012, DOI: 10.1038/mp.2012.158