That's true. It's just that the Dr. said "poison" not poisoning. Too much CSI for me!
My two cents is that HKS kept her in a drug stupor and enabled her drug abuse, which intensified her paranoia and dependence on him so that he could continue to ride the gravy train. If ANS was a happy, healthy, non-whacked-out-on drugs person, she wouldn't have needed him and probably would have dumped him. She would have been free to reach out to all the other people who tried to reach out to her from whom HKS purposefully kept her isolated and ostracized.
Last night on Greta two different people said when Anna was alone with them without Howard she was amazing and open and funny and as soon as he'd show up she was nervous and jumpy and would get surly.