I read in sutta pitaka some ware that says - if some one start doing
satipatthana (meditation), old karma will not effect him much. or if someone reach udaya-waya gnaya, not shure.
anyway if some one is doing satipatthana bahawan continuously most of the suffering that come from the thoughts will disappear according to samadi and vidarshana gnana.
if some one can do up to udaya-waya gnaya (even very lower level) most of the suffering life will fade away, cause he see the nature of appear & disappear in thoughts.
listen to dhamma talks by Ven Uda Iriyagama Dhammajeewa Thero at Nissarana Wanaya, he explains these kinds of things thrue satipatthana (meditation)
http://sinhaladhamma.blogspot.com/
hope this is helpful.