The ROOT "CAUSE" of depression is the IDENTITY CRISIS.
A very important SYMPTOM of
Depression is stress (immense stress) that drains the body's reserves of chemicals, minerals, nutrients, enzymes, etc..
A "symptom" is a 'result', not a CAUSE. Replenishing all of these chemicals, nutrients, etc. does not address the 'cause' of
Depression (which is always UNRESOLVED emotions or psychological/subconscious issues that have been neglected,...example: "baggage", issues).
However, it is your decision of choosing to be partially/temporarily 'cured' empirically/clinically as a 'biological unit' by simply repleneshing whatever chemicals/nutrients are deficient (usually provides only a cure that needs continuous maintenance) or realizing and addressing the psychological/subconscious emotion(s) that was/were always neglected, leading to a permanent and genuine cure which will also establish a SELF/identity and make you a stronger and happier person for life.
I'm convinced that the most common personal problem in the world is the identity crisis. It keeps us from being conscious of who we really are (realizing and establishing a "SELF").
Not being able to discover/establish who we really are also prevents us from BEING the person we are. The result is that we [the individual] can't be a unique and separate person that can relate to reality on a PERSONal level and interact with other people PERSONally.
This has a very subtle and unrecognized effect on the subconscious, and has a multi-faceted effect on everything we do, think, and feel ("pain" is an "emotion"). Since "attitude is everything" (semi-popular expression which is neglected), it is the emotion of insecurity/low self-esteem that causes pain (otherwise we could simply feel "sensation" when we get hurt).
Humanity (as a whole and as individuals) has never really felt comfortable about being imperfect. Humanity/society has always been very prudish about properness/propriety (desiring to be better than the other person by berating them) for the sake of VAIN ego.
So, it is largely for the sake of VAIN ego (many good deeds are done because we have an ego, but VAIN ego damages our own humanity) that we lose touch with who we really are. This betrayal of self is, no doubt, resented by your conscience, and you have only to appease your conscience by realizing SELF (establishing your identity, your true 'NATURE', not merely a 'personality').
So, if you ever had any unrealistic expectations of yourself (vanity), such as...
1) an ambition to be perfect (because other people would berate you for their ego,...or perhaps for their conscience also)
or
2) were ever taught to blame yourself for things that, REALISTICALLY, you had no control over,...
You only have to realize that you were TAUGHT to be unrealistic with your SELF.
Stop accepting shame and guilt for the past, it was GIVEN to you (imposed on you) by those who had a need to get rid of it. Your conscience sees this 'acceptance' as not only thwarting justice by exonerrating the guilty, but also as condemning the innocent (you are the INNOCENT). Do not deny justice it's due. Leave the past to be the past, live in the PRESENT.
FREE THE PRISONER, for the prisoner was always innocent.