To the Editor: In regard to the article by Jacqueline Borg, Psychol., M.Sc., et al. (1), we were intrigued by the potential association between the serotonin system and the character trait of "self-transcendence." However, we urge caution in interpreting these results as evidence of a biological basis for religion/spirituality. A careful definition of terms is required to avoid confusion.

"Spirituality" is a relatively new term that refers to the nearly universal human search for meaning, often involving some sense of transcendence. Some suggest that spirituality is a broader concept than religion and is therefore more appropriate for pluralistic contexts (2). However, it is not clear that spirituality actually describes a more universal phenomenon (3). In fact, the concrete and individualized manifestations of "spiritualities" tend to function not as universals but precisely the opposite: unique religions with only one member (4).

On the other hand, "religion" refers to a particular tradition, practice, or community that shapes a comprehensive world-view sufficient to interpret all of human experience within a specific cultural context (3). Within any religious tradition such as Catholicism, there are many practices that may be considered faithful and normative, such as Benedictine monasticism, "third-order" Franciscan spirituality, or the prayer of the Rosary. Of all the practices of spirituality, a small subset might be called "mystical" or marked by visions, "revelations," or losing the sense of oneself.

Although we doubt a direct correspondence, such mystical experiences may appear similar to the auditory and visual hallucinations induced by psychotropic drugs, such as LSD. Some aspect of such mysticism may be mediated by the serotonergic system. However, Dr. Borg et al. used religion and spirituality interchangeably, and they reduced religion/spirituality to mere mystical experience. This reduction is misguided and potentially confusing. Many faithful religious practices have no mystical component, and in fact, several religious traditions specifically reject the type of mystical experience addressed in this article (5).

Therefore, we suggest that the variability in serotonin may not be best understood as a marker for religiousness, per se, but as a marker for a more general character trait found in both religious and nonreligious people. It would be interesting to repeat a similar study within two populations of religious and secular subjects. We suspect that within both populations, a subset might have lower binding potentials that would correlate not only with "spiritual acceptance" but also with the metrics of mystical experience and perhaps recreational drug use. Finally, given the hypothesis that self-transcendence is environmentally influenced by the differences between Swedish and American cultures, it would be interesting to further test this hypothesis by comparing the results in Sweden and the United States with a population drawn more from the openly mystical contexts found in some African or aboriginal cultures.