Is it better to focus on the out-breath than the in-breath for calming the nervous system?

I read that lengthening the out-breath activates the parasympathetic nervous system. Is this specific focus more effective for treating high anxiety and chronic stress than simply observing the natural rhythm of the full breath cycle? My name is Ramesh, and I am from Ahmedabad. My DOB is 17th November 1985, born at 4:30 AM.