When a person gets old, he starts to blame his depression on some social events or typical circumstances on events that happened. However, after a death of a friend or a person they loved dies or a person died with a chronic illness which is similar to theirs then depression is likely to fall. Science has followed new studies which show the brain imaging of an old person who showed that the brain circuits which are known to have been responsible for mood swing and food, sleep, etc. are to be not working properly while an old person is in depression.

With age, humans tend to deteriorate and become very much likely to have mood swings, change in temper to the hotter side, and other such problems. However, it is nothing new and it very common for you and others who are getting old, to face such issues. You will have to ensure that you try and stay as calm as possible and do things, which you think will make you happy, the rest will be all taken care of by your children, or other care takers whom you may have looking after you.
There are also diseases, which are known to be affecting an elderly to fall under depression a very good aunt of mine had her health problems, and she used to stay very depressed. She went to the doctor and the doctor prescribed her with anti depressants so that she could get back to her life. Depression among the elderly can easily create more space for diseases to enter into them. Which can result them to die depression is also known a very dangerous thing to happen to an elderly. Proper medication should be given to them, and proper psychotherapy should be given so that they recover soon.