It is partly genetic. My mum suffers with anxiety, depression and nerves, and whilst I am the last child of 3, all 3 of us suffer in some respect. Unfortunately I seem to be the worst!
My older sister suffers from depression. My middle sister is pretty much ok but can be moody. I suffer from anxiety and depression.
Developed it in my mid teens and it has plagued my life ever since. My mum has never been able to get over it, so I feel what hope is there for me! BUT we all different, and whilst people never are totally free from fears, you can address them, work around them, and get a better quality of life.