So I would say this is
very offtopic, I didnt realize this yesterday, when the last horror attack formed. But sinc eshanzeek said ok, I'll paste it, its not much anyways.
So first of all it was Kernberg who had the idea that NPD is a form of counterpsychotic function where the grandiose-self structure defends against paranoid-schizoid-level rage and envy. How this works I never was able to figure out because I couldnt grab hold of - cough - an online version of the book

Still I would expect him to think NPD and psychosis are rather contrair and that NPD would protect against psychotic symptoms and it seems I would be right as Ronningstam writes
p 131 wrote:Although grandiosity occurs in both NPD and psychotic
disorders or schizophrenia, the presence of psychotic illness
and loss of reality testing contraindicate a diagnosis of NPD
(O. Kernberg, 1990). Nevertheless, experiences of severe
narcissistic disillusionment can without necessary support
develop into worsening narcissistic psychopathology
(Ronningstam et al., 1995), which in severe cases may
include specific grandiose delusions or paranoid revengeful
reactions.
Kernberg, O. (1990). Narcissistic personality disorder. In
R. Michaels (Ed.), Psychiatry (chap. 18). Philadelphia:
Lippincott-Raven.
Then there are a few mentions of studies elsewhere, which I havent looked at.
Pincus, The PNI wrote:Grandiosity and vulnerability exhibit distinct and substantively meaningful
patterns of correlations across measures of psychopathological symptoms
in both normal and clinical samples. Ellison, Levy, Cain, and Pincus
(2009) found that Grandiosity is significantly associated with presenting
patients’ initial scores for mania and violence and that Vulnerability significantly
predicted presenting patients’ initial scores for depression, psychosis,
and sleep disturbance.
Ellison, W., Levy, K. N., Cain, N. M., & Pincus, A. L. (2009, November). The
impact of client narcissism on psychotherapy course and outcome. Paper presented at
the mid-Atlantic regional meeting of the Society for Psychotherapy Research,
Philadelphia, PA.
ibid wrote:In a student sample, Miller, Dir, et al. (2010) found
that Vulnerability exhibited significant correlations with anxiety, depression,
hostility, interpersonal sensitivity, paranoid ideation, and global distress. In
contrast, Grandiosity only exhibited a significant negative correlation with
interpersonal sensitivity.
Miller, J. D., Dir, A., Gentile, B., Wilson, L., Pryor, L. R., & Campbell, W. K. (2010).
Searching for a vulnerable dark triad: Comparing factor 2 psychopathy, vulnerable
narcissism, and borderline personality disorder. Journal of Personality, 78,
1529–1564. doi:10.1111/j.1467-6494.2010.00660.x
Simonsen, Comorbidity between NPD and Axis 1 wrote:The prevalence of personality disorders in schizophrenia varies greatly in the few studies that
have been carried out (e.g., Newton- Howes, Tyrer, North, & Yang, 2008). Until this century
most data were based on samples of patients with chronic schizophrenia, in which it is likely
that course deterioration has confounded the findings. Prevalence rates for NPD in these samples varied from 5% to 16%. Unfortunately, all relevant studies used retrospective designs and small
samples. Psychotic disorders among inpatients were likely to be diagnosed with personality disorder
in general, as well as more often in association with NPD, although insignifi cant (odds
ratio 2.8, CI: 0.5–14.1) (Oldham et al., 1995). But there were no differences between median
number of personality disorder criteria met for narcissistic inpatients with and patients without
a psychotic disorder.
In a study of 102 recovered schizophrenic outpatients, Oulis, Lykouras, Hatzimanolis, and
Tomaras (1997) found that 15% met criteria for DSM- III- R NPD, whereas Solano and De
Chavez (2000) found a 5% prevalence of NPD in 40 schizophrenic patients. Finally, in a clinical
epidemiological study of 32 fi rst- episode psychotic patients, 16% met criteria for DSM- IV NPD
(Simonsen et al., 2008).
Narcissistic personalities tend to reconstruct reality to match their image, which they are
unable and unwilling to give up. This rigid distortion of reality and their fantasy and illusory
world may make the aloof narcissist vulnerable for psychosis, but little empirical data are available.
Newton- Howes, G., Tyrer, P., North, B., & Yang, M.
(2008). The prevalence of personality disorder in
schizophrenia and psychotic disorders: Systematic
review of rates and explanatory modelling.
Psychological Medicine, 38, 1075–1082.
Oulis, P., Lykouras, L., Hatzimanolis, J., & Tomaras, V.
(1997). Comorbidity of DSM- III- R personality
disorders in schizophrenic and unipolar mood disorders:
A comparative study. European Psychiatry,
12, 316–318.
Oldham, J. M., Skodol, A. E., Kellman, H. D., Hyler,
S. E., Doidge, N., Rosnick, L., & Gallaher, P. E.
(1995). Comorbidity of axis I and axis II disorders.
American Journal of Psychiatry, 152, 571–578.
Simonsen, E., Haahr, U., Mortensen, E. L., Friis, S.,
Johannessen, J. O., Larsen, T. K., . . . Vaglum, P.
(2008). Personality disorders in fi rst episode psychosis.
Personality and Mental Health, 2, 230–239.
Solano, J. J. R., & De Chavez, M. G. (2000). Premorbid
personality disorders in schizophrenia. Schizophrenia
Research, 44, 137–144.