In general, therapists should not diagnose someone who is not their patient without proper authorization or a valid professional reason to do so. Diagnosing individuals requires a thorough understanding of their mental and emotional health, which can only be gained through a proper therapeutic relationship and assessment process.
The confidentiality and privacy of the therapeutic relationship are essential, and sharing information about individuals who are not under their care could be a violation of ethical guidelines and professional standards. Diagnosing someone without their consent or without being their therapist may also be considered an invasion of privacy and may have legal implications.
However, there are some situations where therapists may provide consultation or input on another person's mental health in specific contexts. For example, if a therapist is part of a multidisciplinary team or involved in a case consultation with other professionals, they may contribute their expertise to the discussion. Still, this is typically done with proper consent and adherence to ethical guidelines and legal regulations.
It's essential for therapists to maintain professional boundaries and prioritize the well-being and privacy of their clients. If someone has concerns about another person's mental health, it's better to encourage that person to seek professional help directly rather than attempting to diagnose them yourself.