Are back and shoulder pain always caused by the same thing or can they not be related?

May not be related: Shoulder and neck pain may or may not be related. If it is related it is probably because of a pinched nerve in the neck (we call that cervical radiculopathy) that is referring pain to the shoulder. However a person can definitely have two things separately going on but usually it does not start at the same time. Meaning one usually started before the other.