Much like a lot of mental and behavioral aspects, genetics and the environment both play a role to certain extents. A 2011 study found that people with a certain form of the 5-HTTLPR gene reported higher life satisfaction. Another study done in 2016 pinpointed 3 different genetic variants associated with wellbeing, along with environmental factors of course. Although this research suggests that happiness can be genetic, that is not the only thing controlling it, you are not limited by your genes. It takes a lot of practice but you can take control of your happiness. Some ways to boost your levels of happiness could be to exercise, eat healthier, showing kindness to others, volunteering, laughing (even if its forcefully), and connecting with yourself spiritually. The relationship between happiness and genetics is the same with depression, where its can be inherited but also affected by other environmental factors. The difference is that with depression, when you inherit those traits that make you more susceptible to the disease, you might not experience it until something from the environment triggers it, like the death of a loved one or the changing of the seasons. I think its research like this one that plays a key role in the way our society views mental health. With the knowledge that mental disorders and overall health is not completely controllable by yourself, more people can be more accepting of the concept of mental health and will try to take care of that part of themselves more often.