Bhikkhu Thanissaro's comment might be useful to the current topic: (ref: http://www.accesstoinsight.org/tipitaka ... .than.html
"Some people have interpreted this sutta as stating that there are many experiences that cannot be explained by the principle of kamma. A casual glance of the alternative factors here — drawn from the various causes for pain that were recognized in the medical treatises of his time — would seem to support this conclusion. However, if we compare this list with his definition of old kamma in SN 35.145, we see that many of the alternative causes are actually the result of past actions. Those that aren't are the result of new kamma. For instance, MN 101 counts asceticism — which produces pain in the immediate present — under the factor harsh treatment. The point here is that old and new kamma do not override other causal factors operating in the universe — such as those recognized by the physical sciences — but instead find their expression within those factors. A second point is that some of the influences of past kamma can be mitigated in the present — a disease caused by bile, for instance, can be cured by medicine that brings the bile back to normal. Similarly with the mind: suffering caused by physical pain can be ended by understanding and abandoning the attachment that led to that suffering. In this way, the Buddha's teaching on kamma avoids determinism and opens the way for a path of practice focused on eliminating the causes of suffering in the here and now."