Where should you explain a bad GPA due to truly extenuating circumstances?

[CheddarcheeseMN]

If the school does not provide a place to mention exceptional circumstances, where is the most appropriate place to include them in the application? Or should an applicant never elaborate unless given the opportunity to do so?

The answers have been given above. There is no most appropriate place to include the mental health problems and ideally a recommender could mention the caregiving role you had during freshman year.