Your friend seems to be having a type of psychotic disorder, could be auditory hallucination.We can't exactly tell if its schizophrenia at this stage, more details would be necessary to make that diagnosis. But, your friend definitely needs help and this can't be avoided as he can harm himself or even others. I suggest you tell him to do the following,
- 1. Diversion techniques. Tell him to listen to songs with a headphone, ask him to listen with high volume. In this way the volume will be higher than the songs volume. This is one of the techniques. The next technique is to ask him to read newspaper loudly or books loudly. This will help him to overcome the voice speaking to him.
- 2. Cognitive behavioral therapy. This is a method where you ask him to take command over the voice, whenever the voice asks him to do stuffs tell him to say loudly "STOP" directed to the voice. Ask him to keep repeating loudly how many ever times till the voice goes away.
- 3. You should know that its best if someone is always there with him, as suicidal thoughts can occur. It will give him an emotional support as well.
- 4. He definitely has to be started on anti psychotics, take him to a psychiatrist who will tell you the doses for the medication.
- 5. I also suggest you take him for yoga classes, will give him some positive energy.