Of course its an oversimplification, depression can seemingly come out of nowhere (leading people to question the 'chemical imbalance' and of course our mind is a vast network of chemical signals so they are integral to how the brain works) but other factors usually come into play. I guess the 'can potentially do more harm than good' is the view you want addressed? It could do more harm than good if people complete abandon therapy in favour of medication. Antidepressants should be seen as more of a life-raft to carry people through until (hopefully) therapy can help. Although I agree it can 'potentially' do more harm than good, I'd say in general people taking antidepressants gets them to a stage where they can get more out of therapy and therefore they usually do more good than harm for most people