Another factor can be medications taken for other conditions. Certain drugs, including temporary use of some antibiotics, will aggravate PN quickly and severely. The reverse being that other medications eg: cortico-steroids taken as a low maintenance dose for a different condition may reduce the severity or frequency of symptoms.

As others have said individuality plays a big part in how each person is affected - as do concurrent conditions, seasonal changes, atmospheric changes, stress, fatigue etc.

Minimizing the detrimental factors where possible and maximizing the beneficial is one of the ways we can influence the progress.