Depression can be caused by many factors. If a person has suffered for more than two weeks they should seek professional help (not the elders, because they are not professionals, and can do much harm)
For me personally, being a Witness did add to my bouts of depression. Before being a dub, no depression, during 3 bouts in 19 years, out of the dubs feeling much better.
I can not say if in those 19 years of being a dub, I wouldn't have had a bout of depression, but I will say the help these people give for depression is ZERO. Linking depression to what a person can or can not do for God(the borg.), is criminal. Their head is up their ass on this one, they have no training whatsoever to deal with depression and should direct people to those with training in the matter. I can not think of anything worse that these people can do than to dissfellowship a depressed person and cut them off from their families.
There is one thing worse, hide child abuse to keep the organization looking good