I wonder is my depression is genetics.

My mom had mental illness when she was at my age. When she was my age, she had a mind like a 6 year old. I wonder is my depression is genetics. I started having depression when I was about 20 years old. I'm doing research on depression and to trying to figure out how did I get depression. My mother sister has schizophrenia. My grandfather and my great-grandmother had mental illness too. It seem as if I am more vunerable to depression. I'm trying my best to fight this but as soon as my depression leaves another depression comes back.