No. Some things do cause more mutations of DNA, but they are external factors (like radiation or mutagenic chemicals).
When organisms inbreed, mutations are more likely to become established in the population. Mitochondrial DNA is a little different, because it is passed almost exclusively through the mother--so, if she has a mutation in the mitochondria, she will give it to ALL of her offspring. So, in a small inbred population, that mutation will spread rapidly.