There is no point in confronting a narcissist with your conclusions about their mental disorder; the base of their entire disorder is DENIAL. They cannot see or accept this truth about themselves, because they are absolutely terrified of the dark and empty place inside and do everything they can to protect themselves from seeing it.
Secondly, unless you are a mental health professional that the narc has employed for aid, you are not qualified to make a diagnosis. Let me repeat again: unless the narcissist has specifically asked you, and you are a qualified mental health professional, it is absolutely not your job to share your diagnosis with the narcissist. It would be doing harm, both to the narc and to yourself, to share your conclusions with them.
Finally, one of the most destructive tools in the Narcissist toolbox is a whirlwind of evil known as DARVO:
Deny
Attack
Reverse Victim & Offender
What this means, in a nutshell, is that the Narc will fall back to a very primitive defense mechanism of “NO I’M NOT A NARCISSIST, YOU ARE, and I’M NOT HURTING YOU, YOU ARE HURTING ME!” —if you break it down this way, you see that it is a very immature and childish defense mechanism, but because the narc is an adult with an adult’s intelligence and strength, the DARVO can be a very powerful and very destructive tool; the Narc can and will DARVO to the point of physical or legal attack, bringing legal charges, and doing a very good job of convincing law enforcement and judges that you are the threat. They will take your information on narcissistic abuse and use the terminology to turn everything around to make you look like the narcissistic abuser and themselves look like your victim. They are skilled manipulators and excellent at spinning up a ‘poor me’ story to rally flying monkeys to their side; this is a ‘game’ you cannot and will not win and depending on the malevolence of your narcissist, you stand to lose friends, close and trusting family bonds, your job, your freedom, or perhaps even your life (put a narcissist hand in hand with a dangerously unstable flying monkey, and that monkey can be manipulated into homicide, this is no joke.)
Once you are to a point in a relationship with someone where you believe or realize that they are a narcissist, the most crucial thing for you to do is to make a plan to get yourself safely away from this person. There is no way to win, there is no way to help them, there is no way to make them see what they’re doing is wrong or force them to stop what they are doing. The only person you can control is yourself, so it‘s best to use your self control to free yourself from a relationship with a toxic and destructive person.
Editing to add: Posts tagged 'quora' were originally my answers to peoples' questions on quora.com. They were monetized but I am giving them away for free here.
If you feel inclined to support my writing, here's my paypal
And if you prefer to pay it forward, I recommend Safe Place as an excellent place to support.