Well, any additional supplement may help anxiety, because when we suffer from anxiety we really have problems producing relaxing neurotransmitters, such as serotonin. This requires a whole orchestra of nutrients - not niacin alone. Single remedies such as nutrients or drugs, seldom "cures" anxiety attacks. Read:

Hit or Miss Supplements for Depression at:
http://www.hypoglycemia.asn.au/articles/hit_miss_supplements.html

I think B5 might be better for stress, coping and anxiety :-)