The Little Shaman is a spiritual coach & specialist in cluster B personality disorders, with a popular YouTube show and clients worldwide.
The definition of disabled is "having a physical or mental condition that limits movements, sense or activities." This absolutely applies to pathologically narcissistic people. While their intellectual and physical capabilities are usually not impacted, their emotional abilities are seriously effected. These are people who have the emotional capabilities and understanding of a toddler, or maybe an even younger child. They are either totally possessed by their emotions or so divorced from them that they seem to have none at all.
Underneath, emotion controls everything pathologically narcissistic people do, but because they have such limited understanding of - and sometimes attachment to - their emotions, they may not even be aware of this at all. You will often find that, along with the usual emotional dysregulation we see with narcissistic people, they also cannot articulate their emotions to others and have very little to no understanding of how other people are feeling. This is also very like a child.
Pathologically narcissistic people have arrested emotional development. If you met an adult who had the physical capabilities of a toddler, you would be able to understand that right away. If you met an adult with the intellectual capabilities of a toddler, you would recognize that right away as well. But when someone has the physical appearance and the intellectual capabilities of a grown person, it can be very hard to understand or even see the amount of emotional difficulty that they are having. You may not see it at all until this person becomes upset. This is especially true because they have evolved within their dysfunction to compensate for it in some ways. They've had to in order to survive. Imagine a 2 year old just left on the street to fend for themselves. They would either die or they would learn. Narcissists have learned. They've learned to mimic. They've learned to manipulate. They've learned to try to compensate intellectually for the emotional difficulties that they are having, and to rationalize the decisions they are making based on this dysfunctional process. In other words, instead of growing out of their dysfunction, they've grown into it.
It can help to look at pathologically narcissistic people as disabled, because the frank truth of it is, they are. If someone is pathologically narcissistic, they are usually affected pretty severely by narcissism in most areas of their life. They will often have a lot of trouble with jobs, with authority figures, with relationships of any kind and just generally with life. We often find that they way they perceive things is not how they really are and that in general, their mindset and way of thinking is simply not conducive with social situations or the way life actually works. There are some pathologically narcissistic people who are able to function well in some areas of their lives, but we will usually see problems because of narcissism in at least one major area of their lives and these problems are usually severe. For example, a narcissist may do very well at their job but have very serious problems with interpersonal relationships. They often have problems with addiction and impulse control as well.
One thing it's important to remember though, is that pathologically narcissistic people know right from wrong. They understand that the things they are doing would be considered wrong at least by others, if not themselves, and that is one reason they attempt to hide them. They are able to control their behavior as well. Some people have trouble believing that, but ask yourself if the behavior has ever occurred in a place where the narcissist knew they could not get away with it. The answer is almost always NO.
We should not consider pathologically narcissistic people disabled and unable to help their behavior. We should consider them disabled and unwilling to make any of the changes in their lives that are necessary to deal with their disability. If someone has lost the use of their legs, they learn to use a wheelchair. They make whatever renovations to their home and modifications to their vehicle to accommodate their disability. They don't insist someone else carry them everywhere for the rest of their lives. If someone has lost their sight, they learn to memorize the layout of their house. They learn to count their steps so they know how to get where they are going and back. They learn to use their other senses to help guide them. They don't insist someone else do everything for them. This is what pathologically narcissistic people are doing: they are making their disability everyone else's problem - while at the same time insisting they don't even have one. They insist everyone make all these allowances and special rules for them and their unacknowledged disability, while at the same time claiming that they are not the ones with the problem.
Even though pathologically narcissistic people are emotionally disabled, there are things they could do to make living with it and navigating their lives easier. Their problems are not going to go away, but they can often be managed differently. The right medication can help. Learning new skills to help with emotional reactivity such as reality testing and creating new coping mechanisms can help. Learning to sit with and process emotions can help. There are many things they could do to take a proactive approach to dealing with this problem, even small things such as cutting down on sugar and caffeine intake or eating better food and getting more sleep. It won't cure their narcissism, but it can help with managing their behavior. However, most of them refuse to even acknowledge there is a problem at all in any real way, so nothing ever changes. And it is a refusal, because inside of themselves, they generally know that something is wrong. They may even admit this or make allusions to it from time to time. Facing this head on is not impossible for them, but it is extremely unpleasant and frightening, so they simply refuse to do it. They continue to go through life with no ability to walk, insisting that others need to carry them. There is no way to help a person who does not want to help themselves, and excusing their behavior or rescuing them only makes the problem worse.
If narcissistic people refuse to do the things they could to in order to manage a problem, then there is nothing anyone else can do. It's not up to everyone else in this person's life to make changes and accommodations and allowances for them when they won't even do the bare minimum for themselves. All you can do is make sure you understand the situation so that you can be sure you are not making things worse on yourself.