I'm not suggesting "the memories may be false or distorted" and I agree with your sentiment expressed above.

What I'm saying is that your theory - "I believe past trauma is the root cause and I doubt people have depression if they haven't had some type of experience they would classify as trauma" was proven false in the study I cited.

It found that one in four depression sufferers had no childhood trauma to speak of.

Your (apparent?) explanation for this - that 1 in 4 depression suffers have simply suppressed their trauma memories - has no scientific basis.

It all gives the appearance that you're projecting your own personal experience without providing evidence.