As well as HR, does the the company have an occupational health department/provider? When my husband was having similar problems a couple of years ago he discovered that he could self-refer to his employer's occ. health partners. They were amazing - acted as a go-between with his employers, offered counselling and coping strategies and backed him up every inch of the way.
I'm with the others here too - encourage your friend to keep a log of anything that happens, and you do the same too. Also, if your friend is member of a trade union, then get them on board. If not, it would pay to join one ASAP.
Take care.