Sounds like Boarderline Personality Disorder or BPD to me. It's emotional regulation issues ranging from characteristics or benign to malignant. The anxiety is caused by fast paced thoughts, not having enough emotional release, compulsive thinking , and extreme thinking and thought hopping which is going on in the back of the person's mind even though it may not be relevant to the situation at hand and time. People with mild forms of ADD also have this. Hence "The Jeckyl and Hyde Effect"
