AO3: Reactive and endogenous depression
One limitation of Ellis's ABC model of depression is that it only explains reactive depression and not endogenous depression.
Although many cases of depression can be traced back to a negative life event (reactive depression), lots of cases cannot be traced back to a specific event life event. (this is endogenous depression). Ellis's ABC model can't explain this as it doesn't have an activating event.
This means that Ellis's ABC model can only explain some cases of depression and is therefore a partial explanation.