I think you are correct about the ,"stress", being a factor. I've often thought that stress played a role in some cancers.
The data suggest that the changes in lifestyle on the loss of a spouse impact on the incidence of almost every type of cancer. The effects were so large that a failure to consider marital status in epidemiological studies may be a source to bias. Understanding these lifestyle changes may provide new insight in cancer prevention.
I am a new widow of 8 months and I care for my mom who has dementia. I read a lot.