Memory loss is one of the major signs of depression. It is also often overlooked by people who assume, especially when it comes to older people, that the memory problem is due to something wrong with the brain.
One of the reasons depression is associated with memory loss is a chemical one. Substances called neurotransmitters are thrown off balance during depression, affecting how memories are stored.
Another reason is an emotional one. When you are sad, you tend to color things differently than they really are. As a result, what you wind up remembering is an often inaccurate presentation of what happened.
Here are some of the most common signs of depression.

As you can see, remembering things is difficult when symptoms such as these are present:
Difficulty concentrating, remembering, or making decisions.
A loss of interest in people and/or activities that once brought you pleasure.
A change in eating or sleeping habits.
Feeling tired all the time.
Restlessness or irritability.
Thoughts of death, suicide, or harming yourself
Like anything else affecting your health, depression is a treatable condition. It is critical to seek professional medical help when symptoms become apparent.