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Phytotherapy and psychiatry: bibliometric study of the scientific literature from the last 20 years.

Abstract

In diverse areas of therapy, including psychiatry, increasing interest in herbal medicine has been shown in recent years. Plants have a wide range of traditional uses, but only a few have been approved therapeutically. Moreover, to our knowledge, no bibliometric analyses on medicinal plants used in psychiatry have been carried out to date. We performed a bibliometric study on scientific publication related to phytotherapy in the psychiatry area during the period 1986-2006. Using the platform Embase.com, including the EMBASE and MEDLINE databases, we selected those documents including the descriptors plant *, herb *, phytotherapy *, phytomedicine *, pharmacognosy *, and psychiatry * (with all diagnostic criteria). The plants' indications were selected according to the PDR for Herbal Medicines. As a bibliometric indicator of the production, Price's Law was applied. Another indicator included was the national participation index (PI) for overall scientific production. A total of 21,409 original documents were obtained. Our data confirm a fulfilment of Price's Law related to scientific production on medicinal plants in Psychiatry. This was observed after we made a linear fit (y = 135.08x-466.38; r = 0.92) and another fit to an exponential curve (y = 132.26[e.sup.0.1497x]; r = 0.99). The plants most widely mentioned in the psychiatric literature were St. John's wort (Hypericum perforatum L.; n = 937). and ginkgo (Ginkgo biloba L.; n = 694). The countries with the highest percentages of documents were the United States (29.44%), Germany (9.41%) and Japan (8.75%), and those with highest proportional PI were India (IPa = 0.935) and China (IPa = 0.721). Productivity on medicinal plants in the psychiatry area increased during the period 1986-2006. Nevertheless, documents about therapeutic herbs in this medical field are still relatively few in number.

(c) 2008 Elsevier GmbH. All rights reserved.

Keywords: Phytotherapy; Psychiatry; Bibliometry

Introduction

The use of medicinal plants for the treatment of different pathological disorders has increased considerably in recent years (Mills and Bone, 2000), and this increase may have been accompanied by a rise in scientific production on the topic. In the specific area of mental disorders, the use of St. John's wort (Hypericum perforatum) in affective disorders, of valerian (Valeriana officinalis) in sleep disorders or of kava-kava (Piper methysticum) in anxiety disorders provide clear examples of this phenomenon, extensible to other phytotherapeutic remedies (Donath et al., 2000; Walker, 2006; Kumar, 2007; Sarris, 2007).

Recent studies have confirmed that complementary medicines (including not only herbal remedies, but also food supplements and other organic and inorganic substances) may be used by as many as 54% of patients with psychiatric disorders (Werneke et al., 2006). Likewise, the last 7 years have seen a marked increase in the number of controlled clinical trials and meta-analyses related to the efficacy of medicinal plants in different neuropsychiatric disorders (Vogeler et al., 1999; Stevinson and Ernst, 2000; Akhondzadeh et al., 2001; Whiskey et al., 2001; Pittler and Ernst, 2003; Roder et al., 2004; Linde et al., 2005; Ernst, 2006; Miyasaka et al., 2007). However, despite an extensive literature on diverse pharmacological aspects of phytotherapy in relation to psychiatric disorders, no data are available about the evolution of such scientific production over recent years.

Likewise, the use of bibliometric tools in the area of biomedical disciplines has increased considerably in recent decades (Terrada and Lopez-Pinero, 1991; Cami et al., 1993, 2007; Maltras and Quintanilla, 1995; Lopez-Munoz et al., 1996a). Despite their methodological limitations, bibliometric studies are useful tools for assessing the social and scientific relevance of a given discipline or field (White and McCain, 1989; Bordons and Zulueta, 1999), in that they permit an overview of the growth, size and distribution of the scientific literature in that area over a particular time period (Lopez-Pinero and Terrada, 1992a, b). Indeed, such studies constitute an effective complement for the opinions and judgements of experts in each field, providing useful and objective instruments in processes of the evaluation of the results of scientific activity and offering a more realistic view of it and an indication of trends and of how it might evolve (Cami et al., 1997; Bordons and Zulueta, 1999).

The use of bibliometric indicators for studying research activity in a particular field is based on the premise that scientific publication is the essential result of such activity (Bordons and Zulueta, 1999). Our group has studied, with a bibliometric approach, the evolution of scientific literature in psychiatry by specific research groups (Lopez-Munoz and Rubio, 1995; Lopez-Munoz et al., 1996a), on different psychiatric disorders (Lopez-Munoz et al., 2006a, 2007), on aspects related to the discipline (Lopez-Munoz and Alamo, 1995; Lopez-Munoz et al., 1996b, 2008) and on specific therapeutic tools in the field of psychopharmacology (Lopez-Munoz et al., 2002, 2003, 2006b). Nevertheless, within the specific area of phytotherapy in psychiatry there are as yet no studies analyzing the evolution of scientific production. This provided the motivation for the present bibliometric study, which set out to analyze scientific production in journals with an international circulation on the subject of phytotherapy in psychiatry, covering the period from 1986 to 2006.

Materials and methods

Data sources

The databases used in this bibliometric study were MEDLINE (Index Medicus, US National Library of Medicine, Bethesda, MD, United States) and Excerpta Medica (EMBASE) (Elsevier Science Publishers, Amsterdam, The Netherlands), which are considered the most exhaustive databases in the biomedical field, and which both participate in the Embase.com platform (Elservier B.V., Amsterdam, The Netherlands).

Using remote downloading techniques, we selected documents related to medicinal plants and psychiatry, according to the descriptors shown in Table 1, and always for documents published between 1986 and 2006. The descriptors in the second group, that is, those related to psychiatry, were selected in accordance with the diagnostic criteria of the DSM-IV-R (APA, 2000). We then selected those medicinal plants with indications approved by the German E Commission (Blumenthal, 1998) in the area of psychiatry. The plants' indications had been selected according to the PDR (Physicians' Desk Reference for Herbal Medicines, 2004). For the purposes of this study, we considered all the original articles, brief articles, reviews, editorials, letters to the editor, etc., and all duplicated documents were eliminated. In this regard, the Embase.com platform permits the elimination of items that may be duplicated in each of the databases (MEDLINE and EMBASE).
Table 1. Search strategy

Primary descriptor Secondary descriptor (a)

Plant * Psychiatr * Obsessive--compulsive disorder
Herb * Mental * Stress
Phytotherapy * Mood disorder Eating disorder
Fitoterapy * Depress * Anorexia
Phytomedicine * Dysthym * Bulimia
Pharmacognosy * Manic * Sleep disorder
 Bipolar * Insomnia
 Cyclothym * Hypersomnia
 Anxiet * Dyssomnia
 Panic Parasomnia *
 Phobia * Premenstrual
 Alzheimer Dementia
 Delirium

(a) According to DSM-IV-R diagnostic criteria.


Bibliometric indicators

As the methodological basis for the analysis of the results, we applied a series of the most widely used bibliometric models and indicators. Among the bibiliometric indicators of production applied is Price's Law (Price, 1963). This law, without doubt the indicator most widely used in analysis of the productivity of a specific discipline or a particular country, reflects a fundamental aspect of scientific production, which is its exponential growth. This phenomenon implies a faster pace of growth for science than for the rest of human activities, so that its size would duplicate every 10-15 years. In order to assess whether the growth of scientific production on phytotherapy in psychiatry follows Price's Law of exponential growth, we made a linear fit of the data obtained, according to the equation y = 135.08x-466.38, and another fit to an exponential curve, according to the equation y = 132.26[e.sup.0.1497x].

As an indicator of the publications' repercussion we used the impact factor (IF). This indicator, developed by the Institute for Scientific Information (Philadelphia, PA, USA), is published annually in the Journal Citation Reports (JCR) section of the Science Citation Index (SCI).

Another indicator included in the present analysis is the national participation index (PI) for overall scientific production. The PI reflects the ratio of the number of documents generated by a given country and the total number of documents obtained in the repertoire. Likewise, the PI was correlated with the global PI in biomedical and health sciences (as well as for psychiatry in particular) for the world's 20 most productive countries in the period 1996-2004, according to the results from Cami et al. (2007).

Results

After a study of the journals analyzed for the period 1986-2006, we obtained 21,409 original documents (articles, reviews, editorials, letters to the editor, etc.) dealing with different aspects related to phytotherapy in psychiatry (Fig. 1). Of the total number of documents, just 6.46% appear as classified (according to the EMBASE database) as controlled clinical trials, controlled and randomized trials, Cochrane reviews, systematic reviews or meta-analyses (Fig. 1).

[FIGURE 1 OMITTED]

As can be seen in Fig. 2, over the last 21 years there has been a marked increase in publication related to phytotherapy in psychiatry worldwide. The mathematical fit to an exponential curve, shown in Fig. 2, permits us to obtain a correlation coefficient r = 0.99, indicating 1.9% of variance unexplained by this fit. In contrast, the linear fit of the measured values provides an r = 0.92, and therefore a percentage of unexplained variance of 15.14%. With these data we can conclude that the repertoire analyzed is more in keeping with an exponential fit than a linear one, and that the postulates of Price's Law are fulfilled.

[FIGURE 2 OMITTED]

Fig. 3 illustrates this even better. Analyzing the last three 5-year periods, it can be seen that the cumulative growth in scientific production on phytotherapy in psychiatry for each quinquennium over the preceding one remains constant, duplicating the percentage of documents. Notable features are the cumulative growth of literature on this topic (146.9%) during the last quinquennium (2001-2005).

[FIGURE 3 OMITTED]

Table 2 shows the 20 journals with the highest IF in the area of psychiatry, according to the JCR of 2006, and the participation index (PI) of the documents in our repertoire within the total of documents published by each journal in the analyzed period. The journals that proportionally devote most scientific production to phytotherapy are CNS Drug (PI = 1.15), the International Journal of Neuropsychopharmacology (PI = 0.898) and Psychosomatic Medicine (PI = 0.739). In Table 3, which shows the 20 journals with the highest IF in the context of the scientific study of plants (JCR, 2006), it can be seen that the publications devoting most attention to psychiatric aspects, within our repertoire, are Plant Cell and Environment (PI = 23.31), the Annual Review of Plant Biology (PI = 12) and Plant Physiology (PI = 11.78).
Table 2. Distribution of documents in our repertoire, based on the 20
journals with highest impact factor inn the psychiatry area

Journal Ranking IF JCR Documents PI
 JCR (a) (a) (n)

Archives of General Psychiatry 1 13.936 6 0.192

Molecular Psychiatry 2 11.804 3 0.186

American Journal of Psychiatry 3 8.25 27 0.245

Biological Psychiatry 4 7.154 13 0.199

Neuropsychopharmacology 5 5.889 6 0.225

Journal of Clinical Psychiatry 6 5.533 28 0.451

British Journal of Psychiatry 7 5.436 31 0.373

International Journal of 8 5.184 4 0.898
Neuropsychopharmacology

Sleep 9 5.126 6 0.200

Journal American Academy of Child 10 4.767 12 0.245
and Adolescent Psychiatry

Journal of Clinical 11 4.767 12 0.245
Psychopharmacology

American Journal of Medical Genetics 12 4.463 0 0
part B-Neurosychiatr Gen

Schizophrenia Bulletin 13 4.352 11 0.340

Psychotherapy and Psychosomatics 14 4.333 4 0.260

Schizophrenia Research 15 4.264 3 0.393

CNS Drugs 16 4.211 12 1.15

Journal of Psychiatry & 17 4.100 3 0.392
Neurosciences

Addiction 18 4.088 5 0.146

Acta Psychiatrica Scandinavica 19 3.857 9 0.249

Psychosomatic Medicine 20 3.857 14 0.739

(a) JCR, Journal Citation Report, 2006; IF, Impact Factor; PI,
Participation Index.

Table 3. Distribution of documents in our repertoire, based on the 20
journals with highest impact factor in the plants area

Journal Ranking IF JCR Documents P1
 JCR (a) (a) (n)

Annual Review of Plant Biology 1 19.837 6 12

Current Opinion in Plant Biology 2 10.182 54 7.17

Plant Cell 3 9.868 219 7.63

Annual Review of Phytopathology 4 9.000 3 2.44

Trends in Plant Science 5 8.000 71 8.66

Plant Journal 6 6.565 325 9.90

Plant Physiology 7 6.125 664 11.78

New Phytologist 8 4.245 57 8.07

Plant Cell and Environment 9 4.135 62 23.31

Molecular Plant-Microbe 10 3.936 82 5.19
Interactions

Journal of Experimental Botany 11 3.630 350 1.71

Plant Molecular Biology 12 3.577 412 9.51

Critical Reviews in Plant Cell 13 3.400 - -

Plant Biotechnology Journal 14 3.378 4 7.55

Plant Cell and Physiology 15 3.324 199 11.1

American Journal of Botany 16 2.969 2 6.66

Molecular Plant Pathology 17 2.963 - -

Planta 18 2.963 243 10.73

Theoretical and Applied Genetics 19 2.717 81 5.72

Journal of Phycology 20 2.580 - -

(a) JCR. Journal Citation Report, 2006; IF, Impact Factor, PI,
Participation Index.


Table 4 shows the data on the number of documents in our repertoire for the period 1986-2006 that include the plants approved by the German E Commission, with indications for neuropsychiatric symptoms or disorders. Of these, the plants most commonly mentioned in our repertoire are St. John's wort (Hypericum perforatum) (n = 937 documents), ginkgo (Ginkgo biloba) (n = 694) and ginseng (Panax ginseng) (n = 536). However, those that present the strongest relationship with psychiatry with regard to the total relevant scientific production during the studied period are kava-kava (Piper methysticum) (PI = 31.76), St. John's wort (PI = 26.50) and vitex (Vitex agnus castus) (PI = 22.47). Likewise, this table includes the distribution of the documents according to the countries in which the research or reviews were carried out. It is noteworthy, here, how much attention is devoted by the United States and Germany to St. John's wort, and by China to ginseng. In this regard it should be borne in mind that of the total of documents in our repertoire, 13,284 (62.05%) include the section corresponding to institution and country in which the work took place, which are defined by those of the first author or by the address for correspondence in the case of collaborations.
Table 4. Documents in our repertoire (period 1986-2006) that include
medicinal plants approved by the German E Commission: distribution of
documents for the world's 20 most productive countries in biomedicine
and health sciences, according to Cami et al. (2007)

 Adonis Bugbane Ginkgo Ginseng St. John's
 wort

Documents 2 131 694 536 937

PI 1.61 16.77 15.40 10.97 26.50

TI (a) Nervous Promenstrual Organic Lack of Anxiety,
 heart syndrome brain stamina depressive
 complaints dysfunction moods

Country

USA 1 55 211 169 837

UK - 13 65 38 83

Japan 1 1 41 34 7

Germany - 14 47 15 126

France - 1 3 3 6

Canada - 16 24 23 21

Italy - 6 10 10 26

The - 6 5 4 8
Netherlands

Australia - 1 16 13 22

Sweden - 0 3 6 1

Spain - 0 2 3 6

Switzerland - 0 15 5 15

Belgium - 1 1 2 1

Israel - 1 5 6 3

Finland - 0 0 0 0

Denmark - 0 2 1 0

Austria - 0 1 0 0

China - 1 18 30 1

India - 0 11 24 4

Brazil - 0 9 4 1

 Kava Lavender Hops Melissa

Documents 378 63 52 75

PI 31.76 4.98 7.04 11.54

TI (a) Nervousness, Nervousness, Nervousness, Nervousness,
 insomnia insomnia insomnia insomnia

Country

USA 141 16 6 10

UK 38 11 5 16

Japan 1 0 1 0

Germany 51 1 10 8

France 2 0 2 4

Canada 14 1 1 1

Italy 6 0 1 1

The 1 0 0 0
Netherlands

Australia 9 0 0 0

Sweden 0 0 0 0

Spain 1 0 0 0

Switzerland 3 0 4 2

Belgium 1 0 0 0

Israel 3 0 0 0

Finland 0 0 0 1

Denmark 0 0 0 0

Austria 0 0 0 0

China 1 0 0 0

India 4 1 0 1

Brazil 1 0 0 3

 Passiflora Rauwolfia Valerian Vitex

Documents 89 28 366 89

PI 19.91 8.14 19.15 22.47

TI (a) Nervousness, Nervousness, Nervousness, Nervousness,
 insomnia insomnia insomnia syndrome

Country

USA 12 9 114 27

UK 9 9 29 10

Japan 0 0 10 0

Germany 8 1 21 8

France 7 0 9 2

Canada 2 0 5 1

Italy 5 0 15 0

The 1 0 13 0
Netherlands

Australia 2 0 7 1

Sweden 0 0 4 0

Spain 0 3 5 1

Switzerland 1 0 8 3

Belgium 1 0 1 0

Israel 0 1 1 1

Finland 2 0 2 0

Denmark 0 1 2 0

Austria 2 0 5 0

China 0 0 9 0

India 9 5 11 10

Brazil 3 0 7 0

PI, Participation Index; TI, Therapeutic Indications.
(a) Neuropsychiatric indications approved by Commission E (PDR, 2004).


Among the countries generating research on phytotherapy in psychiatry (of the 20 most productive countries in biomedicine), the most significant, as Table 5 shows, is the United States, whose PI is 29.44, followed by Germany (PI = 9.41), Japan (PI = 8.75), the United Kingdom (PI = 8.09) and India (PI = 7.32). This ranking does not follow a pattern similar to that of the general distribution in the field of psychiatry, since while among the most productive countries in psychiatry are the USA, the UK, Canada and Germany, the countries with the highest PI in the phytotherapy area are China and India. However, if we consider the productivity of these countries in this topic in relation to their overall production in the field of psychiatry, only India, of the 20 largest producers in biomedicine and health sciences (in the period 1996-2004), devotes a higher percentage of attention to the study of phytotherapy in psychiatry (Fig. 4).

[FIGURE 4 OMITTED]
Table 5. Distribution of documents in our repertoire for the world's 20
most productive countries in biomedicine and health sciences

 Country (a) Biomedicine/ Psychiatry Phytotherapy P1
 health (%) (b) in psychiatry
 sciences (%) (c)
 (%) (a)

 1 USA 41.4 49.12 29.44 0.172
 2 UK 10.7 14.29 8.09 0.184
 3 Japan 8.73 1.46 8.75 0.209
 4 Germany 8.02 6.42 9.41 0.268
 5 France 5.84 2.81 5.28 0.201
 6 Canada 4.95 7.13 3.75 0.203
 7 Italy 4.41 2.12 3.45 0.168
 8 The Netherlands 3.20 3.22 1.58 0.131
 9 Australia 2.89 4.97 2.35 0.24
10 Sweden 2.60 2.59 1.48 0.174
11 Spain 2.41 1.15 3.89 0.286
12 Switzerland 1.99 1.57 1.44 0.197
13 Belgium 1.47 0.75 1.13 0.201
14 Israel 1.33 2.08 1.52 0.311
15 Finland 1.26 1.79 0.53 0.141
16 Denmark 1.26 1.32 0.65 0.150
17 Austria 1.05 0.77 1.06 0.259
18 China 1.07 0.92 6.51 0.721
19 India 0.93 0.62 7.32 0.935
20 Brazil 0.86 0.55 2.33 0.480

PI, Participation Index.

(a) The world's 20 most productive countries in biomedicine and health
sciences for the period 1996-2004.

(b) Their productivity in the discipline of psychiatry. Data from
Cami et al. (2007).

(c) n = 13,284 (62.05% of the documents in the repertoire). Documents
with ascription to country of origin.


Discussion

Bibliometric studies constitute interesting tools for assessing the social and scientific importance of a given discipline or topic over a specific time period (Lopez-Pinero and Terrada, 1992a, b; Lopez-Munoz et al., 1996a, b, 2003, 2006a; Garcia-Garcia et al., 2005; Cami et al., 2007). The term "bibliometrics" was introduced in 1969 by Alan Pritchard, to define the application of mathematical methods and statistics to the process of diffusion of written communication in the field of scientific disciplines, through the quantitative analysis of different aspects of this type of communication (Pritchard, 1969). These analyses provide a picture of the growth, size and distribution of scientific literature related to the discipline or topic and of the evolution of both the biomedical speciality, area of specialization or subject in question and the scientific production of an institution, country, author or research group (Bordons and Zulueta, 1999).

Nevertheless, previous studies have drawn attention to a series of methodological limitations characteristic of this sociometric approach (Gomez and Bordons, 1996), since it is obvious, for example, that the international scientific production in a particular field, such as phytotherapy in psychiatry in this case, is much more extensive. In fact, our repertoire includes only those documents found in the databases consulted, and which mention the descriptors we selected. Thus, despite the wide range of descriptors selected, it may occur, for example, that a certain number of articles deals with little-used medicinal plants, or plants still at the initial research stage, so that their possible psychiatric uses are not mentioned in any of the database fields. However, the criteria set by the databases themselves condition the subsequent development of the material to be studied. For instance, many journals are not indexed in the usual databases; this is also the case of contributions made to scientific conferences and meetings (Lopez-Munoz et al., 1996a). But in spite of all the limitations mentioned, the acknowledged quality of the publications included in the databases employed in the present study and their coverage mean that the documents selected constitute a more than representative sample of the international research on phytotherapy in psychiatry.

Taking into account these premises, the design of the present analysis allows us to make a global assessment of the growth of scientific literature in relation to phytotherapy in psychiatry. After making the mathematical adjustments shown in Fig. 2, it was found that the number of publications on this topic has a tendency for exponential growth, in line with Price's (1963) theory of the expansion of scientific literature. This tendency, combined with the absence of a saturation point, points to a promising future for the field, all the more so considering the rather limited involvement of phytotherapy in the area of psychiatry to date. Even so, it is not easy to draw conclusions on this point, since phytotherapy and psychiatry are presented as independent disciplines without any apparent connection, at least as regards the JCR groupings or the data provided in the most exhaustive bibliometric analyses made so far, such as those of Cami et al. (1997, 2007). In any case, the results of the present study appear to concur with those obtained in previous work by our group on different aspects of the psychiatric disciplines, such as bipolar disorder (Lopez-Munoz et al., 2006a), diagnostic criteria (Lopez-Munoz et al., 2008) or antidepressants of the SSRI family (Lopez-Munoz et al., 2002, 2003, 2006b).

Another aspect of interest in relation to scientific production that we have analyzed is its quality. To this end, we used the indicators of impact and excellence of the publications on the topic in question. In order to assess the prestige of a journal, or the quality of a publication, we employed as an indicator of repercussion the impact factor (IF), a dynamic indicator employed since 1971, published in the Journal Citation Reports (JCR) section of the Science Citation Index (SCI) and calculated by the Institute for Scientific Information (Philadelphia, USA) for cataloguing scientific journals. The JCR considers scientific journals by specific area, ascribing to each of them its corresponding IF thus establishing a ranking of "prestige" (Gervas et al., 1990). IF does also have some limitations and disadvantages, such as discrimination against original articles in favor of reviews, higher scores for journals published in English or the unfavorable attitude towards topics covered by a small number of researchers (Lehrl, 1999). Nonetheless, IF is the tool most widely used by the scientific community for assessing the quality of research work or the prestige of a given journal (Garfield, 1979; Lopez-Pinero and Terrada, 1992a). In our repertoires, the fact that such prestigious journals as Plant Cell (IF = 9.868), Plant Journal (IF = 9.565), Plant Physiology (IF = 6.125), Journal of Experimental Botany (IF = 3.630) or Plant Molecular Biology (IF = 3.577) publish articles related to psychiatry is an important factor in this regard, and which indicates the great relevance the topic of mental disorders has acquired in recent years in the field of medicinal plants.

On the other hand, the journals with the highest IF in the area of psychiatry appear to publish fewer studies related to medicinal plants (they have a much lower PI than journals from the field of plants), which may indicate a discrepancy between basic research, more common in plants journals, and clinical research, more common in journals from the field of psychiatry. By way of example, the journal with the highest PI in the area of plants, Plant Cell and Environment (PI = 23.31), covers different aspects of basic research, such as those of biochemistry, molecular biology, biophysics or cellular physiology, together with structural, genetic and pathological aspects related to plants' function. However, journals dealing more specifically with clinical phytotherapy (not shown in Table 3 due to their low IF) have PIs higher than the mean for journals in the plants field, examples being Phytomedicine (PI = 16.6; IF = 1.403), Phytotherapy Research (PI = 10.96; IF = 1.144) or the Journal of Ethnopharmacology (PI = 7.27; IF = 1.625).

Continuing with quality-related aspects, despite the great quantity of documents included in our repertoire, there are very few clinical studies carried out according to quality methodological criteria, such as controlled and randomized clinical trials, meta-analyses or systematic reviews: these account for only 6.46% of the sample. These data support those reported by Kamagate et al. (2005), who reviewed the literature on clinical trials carried out with medicinal plants during the period 1980-2000, identifying just 48 controlled clinical trials, of which 85.4% were randomized, 87.5% were comparative (95.2% versus placebo) and 81.3% employed double-blind methodology. Although the majority of these studies were short-term and with rather small samples, they were nevertheless generally performed in accordance with the recommendations of the World Health Organization.

As shown in Figs. 2 and 3, from the early 2000s we can observe a definitive upturn in publications on phytotherapy in psychiatry. This finding coincides with the launching of St. John's wort as an antidepressant in Germany and the USA from 2000, which might be seen to mark the beginning of the gradual clinical introduction of new medicinal plants for different psychiatric disorders. The scarcity of literature on phytotherapy in psychiatry before the late 1990s may be explained by the fact there was, in general, no need to publish articles in support of the properties of plants, since many of them had well-established traditional uses (Blumenthal, 1998). By way of example, one of the pioneering countries in clinical studies with medicinal plants was Germany; only relatively recently did more publications begin to appear in English. This, combined with the fact that certain journals published in German are not included in the databases used here, may explain this less extensive diffusion of scientific information in the field of phytotherapy (Walker, 2006).

With regard to the PI of the different countries in scientific production on phytotherapy in psychiatry, it should be borne in mind, first of all, that the databases normally used in this type of analysis, as is our case with MEDLINE and EMBASE, only include in their AD section (address of authors) the address of the first signatory or corresponding author. Thus, the PIs of the different countries reported in this study will always be an approximation to the places in which research on phytotherapy in psychiatry is generated, generally a fairly faithful one, but not totally accurate. The small variations with respect to the reality will be determined by the presence of collaborative projects between research groups from different countries (multicenter and multinational clinical trials, etc.). Bearing this in mind, the ranking of producer countries is led by the United States, which generates almost a third of the total scientific production in this field (29.44%). An indication of North-American interest in products of natural origin, as reported by Newman et al. (2003) on the basis of a survey by the US National Cancer Institute (NCI), is that the percentage of small molecule, new chemical entities that are nonsynthetic has remained at 61% (of the 877) averaged over the period 1981-2002 and were inspired in natural products. In second place in the ranking from our study is Germany (9.41%), which has a broad tradition in the use of medicinal plants and has been carrying out clinical studies since the 1980s (European Scientific Cooperative on Phytotherapy, 2003).

Table 5 shows the data from the 20 most productive countries in biomedicine and health sciences, according to a recent study published by Cami et al. (2007), and compares the data for general productivity in the psychiatry discipline with productivity in the specific field of phytotherapy in psychiatry. It is worthy of note how some countries, such as India, Brazil or China, sit near the top of the ranking for phytotherapy production (Fig. 4), reflecting their special interest in research in this field. Only India, though, presents greater proportional interest in the study of medicinal plants in psychiatry than in psychiatric studies per se. Other countries, such as Switzerland, Austria or Belgium, maintain rates of productivity in phytotherapy research that are in proportion with their global index for psychiatry. At the other end of the scale, it is interesting to note the lower relative interest in this specific field, within the context of their general production in phychiatry, of countries such as the United Kingdom, Canada, The Netherlands or Australia.

Given the wide variety of plants employed in medicine, and more specifically in the area of psychiatry, it was considered appropriate in this work to restrict ourselves to studying those plants with the most scientific support behind them, and in selecting them we employed the list provided by Germany's prestigious E Commission. Thus, the medicinal plants with the highest PI coincide with those traditionally most widely used in the different disorders of the psychiatric spectrum, such as kava-kava, valerian and, above all, St. John's wort (Donath et al., 2000; Werneke et al., 2006; Kumar, 2007; Mitchell, 2007; Miyasaka et al., 2007). Even so, the majority of authors call for more research and controlled clinical trials for testing the hypothetical efficacy of all the plants currently employed, within the framework of their traditional uses, in the psychiatric field (Walker, 2006; Sarris, 2007).

By way of conclusion, we can assert that, despite the limitations of bibliometric studies, thanks to the design used we have been able to describe the representativeness and evolution of international research on phytotherapy in psychiatry, taking into account the parameters of quality and diffusion most widely employed at an international level. The results of our bibliometric analysis provide evidence of the exponential growth of scientific literature on this topic, still more commonly found in specialist publications on plants than in psychiatry or psychopharmacology journals. Indeed, the tremendous increase in the amount of literature on this topic and its diffusion in some of the most prestigious scientific journals suggest that the study of medicinal plants in psychiatry is a topic whose development is in full swing from both the basic and clinical research perspectives.

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P. Garcia-Garcia (a), F. Lopez-Munoz (a), *, G. Rubio (b), B. Martin-Agueda (c), C. Alamo (a)

(a) Department of Pharmacology, University of Alcala, Cl Juan Ignacio Luca de Tena 8, 28027 Madrid, Spain

(b) Retiro Mental Health Services, Department of Psychiatry, Complutense University, Madrid, Spain

(c) Teaching and Research Unit, Primary Care Head Office, Guadalajara, Spain

* Corresponding author. Tel.: + 3491 7248210; fax: + 34917248205.

E-mail address: frlopez@juste.net (F. Lopez-Munoz).
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Author:Garcia-Garcia, P.; Lopez-Munoz, F.; Rubio, G.; Martin-Agueda, B.; Alamo, C.
Publication:Phytomedicine: International Journal of Phytotherapy & Phytopharmacology
Article Type:Report
Geographic Code:4EUSP
Date:Aug 1, 2008
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