Hi there! This is a tough question to answer because depression is very individual, so sometimes the reason one person gets depressed (for example, parents getting divorced) can be very different from another person (losing at a football game). Every reason for depression is valid.
Of the people I’ve worked with, the most common reason has been loss of something – whether loss of a family member, a friend, or of a job. Loss of friendships are particularly common, or difficulty managing friendships and relationships. Often a long term goal for the people I work with is to see friends more often and feel accepted.