This article by Ed Hagen has been published on the Grasshoppermouse website. It begins:
“Virtually all mental health researchers accept that Major Depression (MD) is a mental disorder, i.e., a brain dysfunction. I argue that this widespread belief should instead be treated as an untested hypothesis, and further, that this hypothesis is probably false. Instead, most MD in the general population is probably severe but normal sadness or grief. Here are seven reasons why:
Most Major Depression is caused by adversity
Ordinary sadness and grief are caused by adverse events. I suspect that a common view about MD is that it fundamentally different, striking without cause, out of the blue. Most studies of MD do not even bother to measure recent negative life events. There is a consensus, however, that MD, too, is caused in large part by adverse events, and that events of higher severity increase the risk of MD. Many early studies found that about 80% of cases of MD had evidence of at least one adverse event (compared to a much lower rate among non-cases). See Figure 1.
More recent studies using twin designs have found similar results, and additionally show the interaction between adversity and vulnerability factors such as female sex and neuroticism (see Figure 2) …”
You can read more from here.