To ask why some people are diagnosed with depression and others recurrent depression

[Takemebackto]

I know some long term suffers of depression who are diagnosed with with a major depressive disorder. My son has been diagnosed with recurrent depressive disorder. I’ve read that with recurrent depressive disorder these a risk of manic behaviour developing. Is this the case?

It can be, but isn't always the case. This is a newish term for what used to be called BiPolar Disorder. It tends to be cyclical.
I hope he is managing his meds as well as he can and that he and you are coping well. .