It is only recently that the link between dry mouth, caused by medications, including anti-depressants, and tooth decay / gum disease has been more widely known by the general public. However, people that have experience depression have known for a long time that it can take away the enthusiasm for many things in daily life. This includes taking care of your teeth and gums, thereby threatening your oral health.
The article in this link discusses this in more detail. Left unchecked, depression, as with any health issue, can have serious affects on many parts of the body.