Constipation is not a consequence of an emotional disorder, at least not initially. However, a lifetime of bowel problems could make anyone question his sanity, and lose his stability.
If you eat mostly fiber-free foods, such as animal products (e.g. fish, pork, beef, chicken, lobster, cheese, milk, etc.), visible fats (e.g. butter and corn oil), alcohol, and grains that are highly refined (e.g. white bread and white rice), then little will be left to make feces with adequate bulk. Your BM will resemble hard rabbit pellets.