Personality regression
Personality regression can be described as a mental state in which one suddenly adopts an identical personality, set of mannerisms and behaviors to that of their past self from a younger age. This is often capable of making one believe that they are a child again and begin acting appropriately to this belief. There are also anecdotal reports of people speaking in languages which they have not used for many years under the influence of this effect.
Personality regression is often accompanied by other coinciding effects such as memory suppression and ego death. It is a very rare effect that is most commonly induced under the influence of moderate dosages of hallucinogenic compounds, such as psychedelics, most notably Ayahuasca, LSD and Ibogaine in particular as well as certain dissociatives.
Psychoactive substances
Compounds within our psychoactive substance index which may cause this effect include: