How many people hear voices?
It’s actually more common than most of us realise, and it’s not always a sign of Schizophrenia. A Dutch study came out saying 1 in 25 people hears voices. For some they are negative (my father’s were always egging him to harm and hurt – he was a major schizo) while others can actually find them positive and encouraging. While for others like your friend it doesn’t actually invove them and it’s more like being at a party and hearing it go on all around you. What’s important is how the voices affect the hearer, if they are negative things being said or they cause distress to your friend they perhaps they do need to seek some Medical help. There are helplines in the UK http://www.hearing-voices.org/ also there are similar services in other countries. Also try intervoice – http://www.intervoiceonline.org/ which has lots of info and a forum Your friend is NOT alone.
