Can I refuse to sign NWM's authoritization form?

I have just received an “authorization” form from NML, re: disability benefits. It is scary since it says NML has the right to look into everything about me — everything. The language goes far beyond medical information. I have been on disability for 10 years after suffering TBI from an accident where a tour bus ran into the back of the car I was riding in. Very well documented, brain scans showing the damage, years of rehab (it continues still I see a neurologist every six months), and even a jury trial that ended with a unanimous verdict in my favor, agreeing that I have lost the ability to do the job I was responsible for (I ran an advertising agency). Must I sign and return? Are there any cases that have challenged this? I am not concerned about the medical records, they are pretty solid. But have them able to look into every facet of my life is unnerving. Anything I can do? Or should I just sign and send it back? Thanks.