tldr; Was smoking weed for over 10 years, later on started clubbing and mixing weed with stimulants like Ecstasy and Amphetamines, got a drug induced psychosis within 5 months. Symptoms: Auditory Hallucinations, Paranoia, Persecutory delusions - was searching for hidden cameras around me every time I had an episode.

My two cents on this study - it works because the voices you hear are what you think others would think of you in this particular situation. Once you start having a conversation with your voice[s], your expectations (your inner modelling of others) change.