Depression, depending on the severity, is often measured by how long the disturbance has been in your life. Mine is categorized as a major depressive episode in which I was at an extremely low functioning level so length wasn't as important but for yours I believe that the amount of time is important.

It's also good to consider the fact that depression does not equal suicide. Depression is a thing where someone has lost interest in pretty much everything, slowly finds less purpose in everyday, and feels a lack of hope in the future. They tend to extrapolate negative thoughts about the future of themselves and mankind. And they tend to have extremely low self worth. But because of it's ability to permeate through most of our day to day life it can put us at risk of suicide. Most of us would just to prefer to be dead somehow but won't want to commit suicide due to the damage it would cause on our family and friends. Aka if there was some sort of way for us to die valiantly without pain I'm pretty sure quite a few of us would not be here today.