Ego inflation is an effect that magnifies and enhances one's own ego and self-regard, resulting in the person feeling an increased sense of confidence, superiority, and general arrogance.  During this state, it can often feel as if one is considerably more intelligent, important, and capable in comparison to those around them. This occurs in a manner similar to the psychiatric condition known as narcissistic personality disorder. 
At lower levels, this experience can result in an enhanced ability to handle social situations due to a heightened sense of confidence.  However, at higher levels, it can result in a reduced ability to handle social situations due to magnifying egoistic behavioural traits that may come across as distinctly obnoxious, narcissistic, and selfish to other people.
It is worth noting that regular and repeated long-term exposure to this effect can leave certain individuals with persistent behavioural traits of ego inflation, even when sober, within their day to day life.
Ego inflation is often accompanied by other coinciding effects, such as disinhibition, irritability, and paranoia, which can lead to destructive behaviors and violent tendencies.  It is most commonly induced under the influence of moderate dosages of stimulant compounds, particularly dopaminergic stimulants, such as methamphetamine and cocaine.     However, it may also occur under the influence of other compounds, such as GABAergic depressants  and certain dissociatives.
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- Kuypers, K. P. C., Steenbergen, L., Theunissen, E. L., Toennes, S. W., & Ramaekers, J. G. (2015). Emotion recognition during cocaine intoxication. European Neuropsychopharmacology, 25(11), 1914-1921 | https://doi.org/10.1016/j.euroneuro.2015.08.012