assuming this refers to affect (the instantaneous, observable expression of emotion).
"Schwingungsfähigkeit" would be "ability to express changes in emotion" (as opposed to having a blunted or flat affect with significant reduction in the intensity or near absence of signs of emotional expression).
http://www.driesen.com/glossary_a-d.htm

the proper psychologic term might also be "resilience"

Kaisen, are you a native English speaker? It doesn't sound like it. Do you have professional qualifications in this field?

Marianne: looks good. What would you do with

Die affektive Schwingungsfähigkeit (ist) überschießend?

(or anyone else, of course!) -

how about

the affective ability to express changes in emotion (is) excessive?

or

the affective expression of changes in emotion (is) excessive?

Thanks.

"ability to express changes in emotion" ist auf jeden Fall eine gute Beschreibung von "schwingungsfähig".

"resilience" ist keine treffende Übersetzung. Resilience würde ich übersetzen mit "Widerstandsfähigkeit", oder bildlich gesprochen mit "Federkraft".

Hi John - a blunted or flat affect is the loss of the ability to express (changes in) emotion or, to put it another way, lack of emotional reactivity. So the opposite would be "excessive/heightened emotional reactivity" - could you work with that? Or "affective lability"?