My feeling has always been that helicopters don't suffer anywhere near as much as fixed wings from turbulence.
But even so I knew a bloke who had to quit his training because he got airsick at 1 hour after taking off. He could almost set his watch by the regular time frame.
But overall it doesn't seem to be as much of a problem for helicopters. Most of the affects are rotational in the horizontal plane rather than than rolling as the machine weather cocks and I think that is less disturbing on the middle ear where all the conflicts occur which cause the sickness.