Narcissistic personality disorder at it's worst is untreatable as the person with it is incapable of seeing/accepting their behaviour and won't take part in therapy. This was my husband. I would call this a mental health issue as it affects all areas of his work/life/relationships. In a way it's like living with a disability. Does this then mean that their abusive controlling behaviour is excusable as they're unconscious of what they're doing?