Consider the typical progression of a patient with major depression: They usually go through periods of poor appetite and limited food intake, and they systematically show decreases in average stomach acid output. So, their protein intake and digestive capacity become deteriorated.
Protein breakfasts work, - if you work it. Yes, I know what many of you are going to say after that last breakfast post- "Good thinking, been there, just can't do that." The simple solution to breakfast: think "protein," not "breakfast."