Daughter has removed herself from family, gained weight and has negative attitude. what could this be??

A medical or: psychiatric illness, a medical illness with psychiatric symptoms, or maltreatment by a family member that she won't disclose.If she is over 18 & depressed enough to be a danger to herself, she can be committed to a psychiatric hospital involuntarily. Otherwise, you can send her a note that you respect her need for distance, you love her & you'll be there if & when she chooses to reach out.