Background: This study explores the possibility that religious fundamentalism (RF) may be linked to deficits in personality structure, which is in contrast to the general assumption that religiosity and spirituality are positively related to mature personality development. Sampling and Methods: To test this hypothesis, 327 (232 female) college students completed the Multidimensional Inventory for Religious/Spiritual Well-Being together with the Innsbrucker Religious Fundamentalism Scale. In addition, the ‘vulnerable dark triad’ of personality (‘vulnerable narcissism’, subscale of the Pathological Narcissism Inventory; ‘secondary psychopathy’,
subscale of Levenson’s Self-Report Psychopathy Scale; ‘borderline personality’, of the Borderline Personality Inventory) was assessed. Results: In general, the relation between spirituality and healthy personality functioning was confirmed. In addition to greatly overlapping with ‘general religiosity’ (p < 0.001), RF was also relevantly predicted by narcissistic (‘hiding the self’) and borderline (‘primitive defenses’) personality facets (p < 0.05 for both). Conclusions: Based on these preliminary data, we conclude that specific structural deficits in personality might lead to more rigorous variants of religious/spiritual beliefs such as RF. Further research
in clinical surroundings as well as in religious extremist groups is recommended.