Could the perceived stress be a result of the biological stress rather than from mental patterns? Yes, but remember that the biological stress in the first place is caused by mental perception. For example, two separate persons can get more or less stress about the same situation, depending on their mental patterns.
So our mental patterns, how we think about situations and circumstances in life, is a cause of how much actual biological stress we will get. Maybe not the only factor, but it could be a key factor in turning around the whole stress cycle.