But the broadcaster added it had not resulted in the "dramatic improvements" he had hoped for.
Marr travelled to Florida to try a new anti-inflammatory drug to help alleviate some of the effects of the stroke he suffered in January 2013.
He told the Press Association: "It hasn't been 'pick up thy bed and walk' but it hasn't been nothing, either."
Marr had described the treatment - which involved having the drug Etanercept injected into the spinal fluid while hanging upside down - as a Christmas present to himself.
"Although I haven't seen the dramatic improvements that I hoped for, there have been subtle and useful changes which I am going to work on through physiotherapy and exercise over the coming months," Marr said.
"We will tell the fuller story in a BBC documentary scheduled to be broadcast in January."
The TV and radio presenter spent two months in hospital after the stroke and had extensive physiotherapy to help him walk. He remains partly paralysed on his left side.
Writing in The Spectator last week, he said: "I'm not complaining too much: I can work, drink, see friends, paint, listen to music and irritate my children like before. I'm a lucky fellow.
"But I can't run or cycle or swim, and I walk very unsteadily and slowly. I drop things and take ages to get dressed."
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Andrew Marr has said a new treatment he has tried four years after a stroke has led to "subtle and useful changes".