Choose brain & mood supplements only when the question fits a product that supply one or more vitamins, minerals, fatty acids, amino-acid derivatives, or botanicals marketed around cognition, stress, or mood; immune support supplements instead provide vitamins, minerals, botanicals, or other ingredients marketed around immune function, although immune effects are ingredient-specific and no broad supplement category can guarantee prevention, treatment, or cure of infection.
The categories separate most clearly through different mechanisms. For brain & mood supplements, examine active ingredient and standardized extract; for immune support supplements, examine immune function and nutrient status. Secondary features deserve weight once the primary purpose is known.