many of the negative symptoms may have been simply correlated with nostalgia

Perhaps the most famous example of this was captured by French author Marcel Proust.He described how tasting a madeleine cake
he had not eaten since childhood triggered a cascade of warm
and powerful sensory associations.So what caused such a major
reversal in our view of nostalgia?Part of it has to do with science.
Psychology shifted away from pure theory and towards more careful and systematic empirical observation.So professionals realized that many of the negative symptoms may have been simply correlated with nostalgia rather than caused by it.