Seeking expert counseling is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
Because his self inflicted cut (I assume it was not an accident), they treated him as if he might have been suicidal. They have to be thorough in cases like this to make sure that he is not suicidal, and if he was, or even if he was inflicting injury on himself without being suicidal, they always cover their liability by checking.
(Is it possible that he has Borderline Personality DIsorder
To make a proper diagnosis, it was necessary to test for various causes for his behavior.
They were looking to see if his behavior was influenced by any drug use. It is their responsibility to protect the patient. If he tested negatively then they have narrowed the cause of his behavior down to other problems. They might have tested to see if he had some chemical imbalance through brain malfunction or disease or injury, once again to be thorough and to protect the patient.
The reason he cut himself could have been due to the fact that he did
NOT take his antidepressant and was getting a "withdrawal" (discontinuation) side effect. They may not have been checking for that, but that could have been what triggered his cutting himself.
They will not report him if they find an illicit substance.
I hope he is feeling fine now.
Elliott Sewell, LPCC, NCC