I'm not familiar with the research, but from experience, you can change it without a doubt. Happiness is an outcome, if you change things that prevent it then you'll have better chances of achieving it.

Tons of money alone is not a guarantee of happiness, there's a cutoff of income beyond which happiness maxes out. Getting seriously ill can of course induce depressive traits, however I've just seen a documentary about using psychedelics for cancer patients and it did improve their lives significantly, although not curing cancer itself.