What are the benefits of using physiological variables in counselling assessment?

What are the benefits of using physiological variables in counselling assessment?

Information helps empower people to develop and grow, and results obtained from psychological assessment can help people be more informed as to how to proceed with utilizing their cognitive and/or emotional strengths to help improve their mental health overall.

Can you think of any limitations to this approach?  What are some ethical implications?

(note : the topic relates to CBT .i.e :cognitive behavioural therapy )