Psychoneuroimmunology in the present:
The state of publications in the field

Pablo Vera-Villarroel & Ana María Fernández1

Resumen
La Psiconeuroinmunología (PNI) es un campo de investigación que concierne las relaciones direccionales entre el cerebro, el comportamiento y el sistema inmunológico. En un esfuerzo por afirmar el estado actual del campo, analizamos la producción científica de la PNI utilizando el sistema más reconocido de productividad científica, ISI red de conocimiento SM de acuerdo al siguiente análisis: Publicaciones sobre PNI, por país de origen, año, autores principales, diarios, y el lenguaje de la publicación. Los resultados muestran que en 1987, el campo produjo 4 artículos, incrementando a un total de 47 artículos en el 2004. Los tres autores más productivos en el área son Glaser, Ader y Maes. La institución más prolífica es la Ohio State University (con 33 artículos). Los tres diarios que publican el mayor número de artículos son: Brain Behavior and Immunity, Psychosomatic Medicine y Psychotherapy and Psychosomatics.
Los resultados son prometedores en términos de producción científica, mostrando que la importancia interdisciplinaria de la investigación en PNI está en crecimiento.

Introduction
Psychoneuroimmunology (PNI) is a field of research that is concerned with bi-directional relationships between the brain, behavior and the immune system. Therefore, its main interest is been to demonstrate the influence and communication between the central nervous system and immune responses.
Compared to other areas of health science, PNI is rather an emerging field in psychology and health. Beginning with the work of Ader & Cohen,1 there have been diverse findings on the relationship between psychology and immune functioning. These authors demonstrated that immune responding could be conditioned by associative learning of a sweetened solution and an immune activated drug. In this way, rats who had experienced this association responded to the stimuli with an overall diminution of immune response. Potential applications of this finding are quite extended, since it points to the postulation that the immune system may respond to learning principles in the same way that motor learning operates.2,3
In research with humans, it has been found that situations involving stress or anxiety, such as depression, taking care of the ill, death of a family member, and the like; are related to immune functioning. Similarly, psychological variables such as perceived stress and attributional styles appear to be related to immune functioning in different populations, for example people who are undergoing the symptoms of HIV-AIDS and the elderly.4,5
Although PNI is a flourishing area of research, it is a field that has been hard to establish in the discipline. However, due to a serious commitment from its proponents to science and empirical research, PNI is becoming a productive area of multidisciplinary exchange among most health researchers.6
In an effort to assess the present state of PNI as a field, and as way to determine its impact on the Spanish speaking community we analyzed the scientific production of PNI using the most recognized system of scienti fic productivity, ISI web of knowledge SM, In this way we present an analysis of publications in PNI in terms of country of origin, years, principal authors and journals, as well as informing of the language of publication.

Method
Unit of Analysis
We accessed the ISI web of knowledge SM database (that includes access to the Science Citation Index Expanded, Social Sciences Citation Index and Arts & Humanities Citation Index) from the virtual library service offered to faculty and students of Universidad de Santiago, Chile; and we evaluated all of the indexed publications dating from 1988 to 2005.
We proceeded to do a search using the keyword “Psychoneuroimmunology,” and obtained the results we present below, organized by different variables.

Year of Publication
It is possible to observe in Table 1, that the distribution of publications in the area of PNI starts with four article in 1987, a pattern that is maintained in 1988, to increase to a maximum of 61 articles per year in 1997 and 1998. Then in 2003, 60 articles in PNI are published, to end with a total of 47 articles in 2004. It is necessary to advise that the number of publications in 2004 may vary, since the data were gathered on the first week of 2005, leaving room to a short period of time between an article’s publication and database entry. Therefore, the indicator for 2004 may vary in future analysis.

Most productive authors
The results of the search yielded a total of 1679 authors publishing in PNI. In Table 2 appear the 10 authors that are most productive in the field, from which is possible to distinguish Glaser, Ader, and Maes with 21, 17 and 12 articles respectively. It can be observed that the number of articles published among the most productive authors ranges from a minimum of 9 to a maximum of 21 publications in PNI per author.

Language of Publications
Table 4 shows the number and percentages of publications on each language. Most of the articles are published in English (91.3%) and only a 1,5% of the articles are in Spanish. This is a predictable trend, since most of ISI publications are in English. In Table 5 appear all the 10 articles in PNI that are published in Spanish.

The most prolific journals in PNI Finally, the most productive journals are presented in Table 6. As one would expect, the journal that publishes the higher number of articles is Brain Behavior and Immunity, (68 articles) which is a publication exclusively concerned with PNI. Following, Psychosomatic Medicine and Psychotherapy and Psychosomatics had a total of 42 and 14 articles respectively.

Final Commentary
Research in psychoneuroimmunology has risen from a few publications in 1988 to a production of over 40 articles per year since 1996. According to the present analysis most scientific reports in the field are prepared in the

English language. This doesn’t mean that other languages are not concerned with PNI, but rather it shows that most research in the field is published in English. It is important to note that Ohio State University is responsible for more than half of the production in the area, which is remarkable in terms of institutional interest in PNI, although it clearly warrants an overrepresentation of its research proclivities in the field.
Finally, the results are promising in terms of scienti fic production in the field, showing that from a modest total of four publications per year, a decade ago, the interdisciplinary importance of research in PNI has raised over a thousand percent.

References
1. Ader R, Cohen F. Behaviorally conditioned immunosuppression. Psychosomatic Medicine 1975, 37: 333-340.

2. Vera-Villarroel PE, Buela-Casal G. Psiconeuroinmunología: relaciones entre factores psicológicos e inmunitarios en humanos. Revista Latinoamericana de Psicología 1999, 31: 271-289.

3. Barra E. Influencia del estado emocional en la salud física. Terapia Psicológica 2003; 21, 55-60

4. Kopnisky KL, Stoff DM, Rausch DM. The effects of psychological variables on the progression of HIV-1 disease. Brain Behavior and Immunity 2004, 18: 246-261.

5. Bouhuys AL, Flentge F, Oldehinkel AJ, van den Berg MD. Potential psychosocial mechanisms linking depression to immune function in elderly subjects. Psychiatry Research 2004, 127: 237-245.

6. Aldwin CM, Park CL. Coping and physical health outcomes: An overview. Psychology and Health 2004, 19: 277-281.

7. Morera A, Casariego C, Valenciano R, et al... Bipolar Affective- Disorder And Hematologic Changes - A Discussion Of Negative Results. Archivos de Neurobiología 1993, 56: 67-71.

8. Bayes R, Borras FX. Contributions Of Experimental-Psychology To The Analysis Of The Placebo-Effect. Revista Latinoamericana de Psicología 1993, 25: 345-363.

9. Ardila R. Experimental Analysis Of Behavior And Health Psychology. Psicololgía Conductual 1997, 5: 435-443.

10.Mustaca AE. Fast Bi-Phasic Responses To Frustration And Euphory. Revista Latinoamericana de Psicología 1999, 31: 133-149.

11.Guarino L, Gavidia I, Antor M, et al Stress, Mental Health And Immunological Changes In University Students. Psicología Conductual 2000, 8: 57-71.

12.Vera-Villarroel PE, Alarcon S Excitatory And Inhibitory Conditioning Of Two Physiological Responses In A Group Of Rats. Psicothema, 2000, 12: 466-470. 13.Espinosa E, Bermúdez –Rattoni F... Behavior-Immunity Relationship: The Role Of Cytokines. Revista de Investigación Clínica, 2001, 53: 240-253.

14.Ortiz VG. Relationship Between Stress And Immunity. A Critical Vision Of Research. Revista Latinoamericana de Psicología 2000, 32: 31-45.

15.Pellicer O, Salvador A, Benet IA. Effects Of An Academic Stressor On The Psychological And Immune Response In The Young Males. Psicothema, 2002, 14: 317-322.