Basis of the theory

"When introversion was first identified by Carl Jung, the Swiss psychiatrist famous for analytical psychology, the focus was on all the mental energy that introverts use up when socializing," Dr. Dow says. "I've also seen my own introverted patients experience a depletion of physical energy when socializing too much. This is why introverts need alone time. That combination of both mental and physical energy depletion is what I would identify as the 'introvert hangover' despite the fact it's not a recognized diagnosis."