As the body recovers from a night of drinking, a hangover creates a state of physiological stress. This manifests with increased cortisol (stress hormone) levels, increased blood pressure and heart rate – changes that typically accompany the experience of anxiety. The brain is also affected by bio-chemical changes; the amount of available endorphins and dopamine (key neurotransmitter involved in reward, learninig and, among others, in regulating anxiety) is lower during a hangover, reducing the system’s natural capability to cope with anxiety. This heightened physiological stress state makes it more difficult for someone to cope with any additional stress that may happen throughout the period.
Link to the full article from Neurosciencenews.com is here