Multivariate analysis of five homoeopathic medicines in a psychiatric population

British Homoeopathic Journal October 1995, Vol. 84, pp. 195~02

Multivariate analysis of five homoeopathic medicines in a psychiatric population

JONATHAN DAVIDSON, MD,* MAX WOODBURY, PHD,t ROGER MORRISON, MD,w JONATHAN SHORE, MD,w GREG BEDAYN, RSHOM (NA)w

Abstract Grade of Membership Analysis (GoM) is a multivariate statistical technique developed for the purposes of medical classification. It was applied to the drug picture concept of homoeopathy, assessing five common medicines with particular applic- ability to anxiety. These were Arsenicum album (Ars), Gelsemium (Gels), Argentum nitricum (Arg-n), Lycopodium (Lyc) and Sulphur (Sulph). The patient sample comprised 104 psychiatric outpatients with structured clinical interview- based primary diagnoses of social phobia, panic disorder, post traumatic stress disorder, obsessive-compulsive disorder, major depression and dysthymia. A homoeopathic screening questionnaire (HSQ) was used to test the integrity of the five drug pictures. Four pure types emerged, providing some evidence to support distinctions between Sulph and Arg-n features, and a pure type with many features of Ars, Arg-n, Lyc and Gels. The fourth pure type contained few of the drug's characteristics. There was some evidence to suggest that psychiatric diagnoses assorted differentially, based on the homoeopathically determined pure types. This study provides qualified support for the drug picture descriptions.

KEYWORDS: Anxiety; Questionnaire; Structured interview; Grade of membership analysis; Homoeopathic types

Introduction In homoeopathy, the choice of an individual medicine is based on the total presenting picture, which includes not only symptoms, but personality, behaviours, fears, preferences for weather, temperature, diurnal variation, food etc. Homoeopaths believe that each homoeopathic medicine induces a certain set, or cluster, of features when given to healthy subjects and that when these are found in the patient, the medicine which produces such features in

* Department of Psychiatry and Behavioral Sciences, I Center for Demographic Studies; both at Duke

University Medical Center, Durham, NC, USA. w Hahnemann Medical Clinic, Albany, CA,USA.

the healthy person would be the medicine of choice for the diseased person. Whether or not these drug pictures truly exist has not been tested empirically, nor is it known whether they may correspond to certain disease states. It is the intent of this report to present pilot data using a multivariate procedure to evaluate five drug types in a population of patients with anxiety or depressive disorders who had taken part in clinical treatment studies. Selection of drugs for this particular project was based on their relevance to social phobia, a commonly found psychiatric disorder, which is of interest to us. The questionnaire was given to patients with social phobia and to groups with other anxiety or depressive disorders.

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Methods Two of us (RM and JS), both experienced clinical homoeopaths, identified five major h o m o e o p a t h i e med ic ines which were believed relevant to the assessment and treatment of people with phobic anxiety disorder. These were Arsenicum album (Ars), Gel- semium (Gels), Argentum nitricum (Arg-n), Lycopodium (Lyc) and Sulphur (Sulph). The number of potential medicines for any disorder in homoeopathy is extremely large, but characteristically practit ioners treat most people with a limited number of commonly used medicines, and these five were chosen as being representative for the population of interest.

For each medicine, the homoeopaths indicated a limited number of features which, in their opinion, were considered to be characteristic and/or discriminatory. In some cases, a feature could be shared by more than one of the medicines. A 33 item scale was developed, each of these items being rated on an analogue scale from 0 to 10. One of the items (19) comprised sub-questions relating to indi- vidually feared situations. Scores at each end of the scale represent the clear, unambiguous presence or absence of a feature. Two excep- tions to this relate to items 16 and 17, in which each score refers to a t ime of day when the subject either feels best (16) or worst (17).

Psychometric properties of the scale have not yet been tested, but the purpose of this report is to present pilot data on what we believe to be one of the first empirical tests of this type, which might best be regarded as a form of validation. At this stage, it is viewed as deriving from clinical validity, which might partly be confirmed if it could be shown that the drug types correspond to certain diagnostic patterns, and if they show differential groupings.

We regard this study as illustrative of what could eventually become a productive collab- oration between academic investigators and clinical practitioners of complementary medicine. Despite our cautions about the early developmental stage of this questionnaire we thus believe the findings to be newsworthy. Patients were asked to complete the scale with reference to their general state most of the time, and to discount any brief changes in

state which may have held true at the time of

completing the questionnaire. In other words, the intent of the questionnaire was not to measure transient symptoms but more the enduring characteristics of an individual. This is referred to in homoeopathic terminol- ogy as 'constitutional' assessment.

Ten items corresponded to features of Ars, 12 to Arg-n, nine to Lyc, eight to Sulph and seven to Gels. Seven items were shared, three by three medicines, and four by two medicines.

Subjects Patients were drawn from the principal inves- tigator's practice, all of them having taken part in various clinical treatment studies. Diagnoses were determined by the Structured Interview for Diagnostic and Statistical man- ual (SCID) 1 and fell into the fo l lowing groups: social phobia, panic disorder, post traumatic stress disorder, obsessive-compulsive disorder and major depression or dysthymic disorder.

Statistical analysis Grade of membership analysis (GoM) was used to evaluate the five medicine profiles. GoM has been developed for assessing cate- gorical data on disease, 2 and has been used by us previously in two classification studies of depression and anxiety. 3, 4 Its properties and differences from other multivariate techniques for classification have been described by us in the above-mentioned GoM studies. Our experience from the two previous studies is that the technique is robust and can be replicated. It also provides information On the classification of the features themselves and on the division of individuals into these clas- sified feature-based types. In this regard, GoM simultaneously accomplishes the sepa- rate tasks performed by factor analysis and cluster analysis. A drawback common to these latter two techniques is that they assign group membership as an all-or-none event, whereas in real life membership is often partial and multiple. This would be particularly applicable to such phenomena as personality characteristics and disease typing. By use of fuzzy set logic, GoM classifies symptoms and/or people into partial membership of groups, hence its name Grade of Membership. Further details of GoM may be found elsewhere. 5 Assor tment of features into the

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i l lness ( ' p u r e ' ) types is represented by the symbol ~,. Grade o f individual membership in pure types is represented by the symbol g~, and ranges from 0.0 (complete lack of membership) to 1.00 (exc lus ive and total membersh ip ) . Most individuals have partial membership in different groups, represented by a score o f > 0.0 and < 1.0.

The GoM derived pure types are obtained from internal variables drawn from the HSQ. Once the pure types have been established, their relationship with external variables can be examined, in this case with reference to age, sex and SCID diagnos t ic category�9 A ser ies o f l i ke l i hood ra t ios are ob ta ined in order to assess the optimal number o f pure types from the data, starting with a comparison o f one versus two pure types. )~2 values are obtained and i f they are significantly different additional hypothesized pure types are tested to see i f there is further improvement in fit o f the model to the data. Once the number o f pure types is decided, the G s are calculat-

�9 IK ed for grade o f membershtp, and the lambdas are assessed to characterize each pure type.

R e s u l t s 104 pa t i en t s were i n c l u d e d in the ser ies . 60.5% were female and 39.5% male. Mean age was 43.0 • 8.7 (SD) years. Diagnostic- a l ly , the sample was c o m p o s e d o f 27 .8% with major depression, 1.9% with dysthymia, 9.6% with obse s s ive - compu l s ive disorder , 15.3% with panic disorder, 5.8% with post t r aumat ic s t ress d i so rde r and 39 .5% wi th social phobia.

GoM analysis was applied to the data set, tes t ing the op t ima l number o f pure types . Log l i ke l i hood ra t ios were ob ta ined for a series o f potential solutions (Table 1), begin- ning with a comparison o f 1 vs 2 pure types. Further log l ikel ihood ratios were calculated for 2 vs 3 pure types, 3 vs 4, and 4 vs 5 solutions.

Pure df log Alog ~2 Fishers t types likelihood likelihood

5 2252 1459.1 229.9 459.9 -3.30 4 1686 1265.2 336.6 733.2 6.45 3 1122 898.5 898.5 1797.1 12.59 1 0 0

TABLE 1. Log likelihood ratio tests for different numbers of pure types

As shown in Table 1, the addi t ion o f each pure type was found to improve the model up to 4 pure types. A comparison o f 5 vs 6 pure types failed to result in a significant ~2 value. The number o f cases in each pure type, and the distribution o f GoM scores are shown in Table 2.

Table 3 describes the features of each pure type based on the contents of the HSQ, and reflected in the lambda scores. Because each HSQ item was rated on an 11 point analogue scale, we deemed it desirable to reduce the number of possible data points to a manage- able amotmt for tabulation purposes and have grouped each o f the items into scores ranging from 0 to 3, 4 to 7 and 8 to 10. Scores of 0 to 4 and 8 to 10 might be considered to reflect best the unambiguous and clear absence or presence of particular characteristics, which is what we are most interested to demonstrate at an everyday clinical level when assessing a patient.

Tab le 4 p resen t s the l a m b d a va lues for external variables in each pure type. Inspection o f the internal var iables for each pure type shows the following characteristic profiles.

Pure type 1 is character ized by a greater degree o f health worries (Ars), fears o f death (Ars), panic a t tacks (Ars), t endency to be cold natured (Ars), fears related to survival and security (Ars), impaired self-confidence (Lyc, Gels), desire for sweet snacks (Arg-n, Lyc), a sense o f b l o a t i n g f o l l o w i n g food (Lyc). Some d iu rna l pa t t e rns were noted , with a tendency to be worst between 1.00 and 3.00 p.m. and i m p r o v e m e n t be tween 3.00 and 5.00 p .m. (Lyc), a g rea t e r d e g r e e o f exhaustion upon waking after sleep (Lyc) was also noted. High levels o f stage fright (Lyc, Gels), a slight increase in the fear of cancer (Ars) were all observed, and fear o f lateness

Pure type 1 2 3 4 n = 25 n - 28 n - 26 n = 25

(gIK) r a n g e

0.0 55 53 51 52 0.0001-0.2499 11 7 11 15 0.2500~.4999 17 19 24 17 0.5000-0.7499 11 13 6 7 0.7500-0.999 2 2 3 3 1.000 8 10 8 10

Totals 104 104 104 104 TABLE 2. Distribution of subjects' GoM scores (gt0 for each pure type


Characteristic Overall 1 2 3 4

1 Tidiness of office-living space (Ars) 0-3 13.7 0.0 20.7 15.0 19.0 4-7 69.0 84.0 66.7 67.9 58.0

8-10 17.3 16.0 13.7 17.1 23.0

2 Importance of doing things properly (Ars) 0-3 1.9 0.0 0.0 0.0 8.4 4-7 46.1 37.8 59.7 39.7 39.5

8-10 52.0 62.2 40.3 61.5 52.1

3 Thinking may have serious health problems (Ars) 0-3 51.0 0.0 78.9 40.4 89.4 4-7 40.1 78.7 21.1 47.6 10.6

8 10 8.9 21.3 0.0 12.0 0.0

4 Fears of death (Ars) 0-3 58.4 10.3 72.3 60.8 89.1 4-7 36.8 76.1 27.7 33.6 10.9

8-10 4.8 13.3 0.0 5.6 0.0

5 Panic attacks (Ars) 0-3 53.8 12.7 63.6 47.4 92.0 4-7 31.9 41.2 26.6 51.7 4.7

8-10 14.3 46.1 9.8 3.9 4.3

6 Preference for cold or hot drinks (Ars, Lyc, Sulph) 0-3 68.l 57.5 70.5 52.7 89.4 4 7 20.0 30.9 24.6 25.4 0.0

8 10 11.9 11.6 4.9 21.9 11.6

7 Importance of issues of survival and security (Ars) 0-3 5.7 5.8 0.0 0.0 20.1 4 7 43.9 21.0 62.0 49.0 36.8

8 10 50.4 73.2 38.0 51.0 43.1

8 Sense of confidence (Lyc, Gels', Sulph) 0-3 22.0 35.2 29.9 10.8 8.9 4 7 55.0 61.0 56.8 65.5 29.4

8 10 23.0 3.8 13.4 23.7 62.7

9 Generally cold or warm natured (Ars, Sulph) 0 3 24.0 55.0 16.8 18.2 6.7 4-7 47.0 29.7 52.7 59.6 44.3

8-10 29.0 15.3 30.5 22.2 49.0

10 Feel insecure (Ars) 0-3 31.9 0.0 29.4 23.4 82.7 4-7 47.5 56.1 49.0 69.2 17.3

8-10 20.6 43.9 21.6 7.4 0.0

11 Others aware of your insecurity (Lyc) 0-3 51.2 44.6 48.1 40.2 71.5 4-7 51.2 44.6 48.1 40.2 71.5

8 10 3.9 11.1 0.0 0.0 5.4

12 Desire for sweet snacks (Arg-n, Lyc) 0-3 22.2 24.4 27.2 8.4 26.6 4-7 52.8 29.6 47.2 66.0 55.0

8-10 25.0 46.0 25.6 25.6 18.4

13 Desire for salt (Arg-n) 0-3 29.6 54.3 21.0 25.9 23.4 4-7 60.9 45.7 68.7 53.5 72.6

8-10 9.5 0.0 10.3 20.6 4.0

14 Desire for cheese (Arg-n) 0-3 38.0 53.7 28.0 15.0 56.4 4-7 48.5 27.2 65.3 75.0 24.0

8 10 13.5 19.1 6.7 10.0 19.6

15 Bloated after eating (Lyc) 0-3 32.7 15.3 10.8 37.0 60.0 4-7 52.9 52.4 80.0 51.8 32.2

8 10 14.4 32.3 9.2 11.2 7.8



16Time of day feels worst (Lye.)

17Time of day feels best (Lyc)

18 Feeling refreshed on waking (Lyc)

1 3 p.m. 21.2 46.7 17.5 15.6 4.7 4-7 p.m. 27.5 19.9 27.3 35.0 29.7

8 10 p.m. 4.3 8.5 0.0 9.8 9.9 none 47.0 24.4 55.0 39.6 65.6

3 5 p.m. 20.4 44.9 0.0 43.2 0.0 (~9 p.m. 23.4 27.1 35.9 21.6 10.8

10-12 p.m. 10.3 17.5 10.8 4.0 10.5 none 45.9 0.0 53.3 31.2 78.7

0-3 43.6 64.6 38.4 22.1 47.0 4-7 49.6 30.7 57.9 77.9 27.7

8 10 7.8 4.7 3.7 0.0 25.3

19Most intense fears 0 3 21.3 3.1 21.5 14.7 51.6 a) stagefright (Lyc, Gels') 4-7 28.7 4.5 40.7 39.5 37.6

8 10 50.0 91.4 37.8 45.8 10.8

b) heights (Arg-n, Sulph)

c) cancer (Ars)

20 Anxious if late for appointments (Arg-n)

21 Introverted or extroverted (Arg-n)

22 Concern for other people (Arg-n)

23 Suggestibility (Arg-n)

24 Impulsiveness (Arg-n)

25 Feel like jumping from high place (Arg-n)

26 Anxiety before meetings or patty or appointment (Arg-n, Gels')

27 Bad reaction to eating sweet foods (Arg-n)

0-3 34.4 36.0 17.0 10.8 70.1 4 7 36.9 44.1 67.0 26.3 7.0

8-10 20.2 19.9 16.0 62.9 22.9

0-3 43.5 0.0 41.0 44.2 76.1 4-7 36.3 62.7 59.0 10.6 20.4

8-10 20.2 37.3 0.0 45.2 3.5

0-3 4.7 0.0 0.0 13.3 5.8 4-7 69.2 49.8 89.1 69.0 77.0

8-10 26.1 50.2 11.9 17.7 17.2

0-3 54.8 61.0 58.7 54.8 41.4 4-7 36.5 39.0 41.3 37.8 25.1

8-10 8.7 0.0 0.0 7.4 33.5

0-3 3.9 12.4 3.9 0.0 0.0 4 ~ 53.0 25.6 83.0 36.8 68.4

8-10 43.1 62.0 13.1 63.2 31.6

0-3 41.8 39.2 35.8 25.9 68.9 4-7 43.9 30.7 61.1 45.3 31.1

8-10 14.3 30.1 3.1 28.8 0.0

0-3 39.7 15.5 36.4 31.8 71.4 4-7 46.7 38.9 57.5 68.2 23.8

8 10 13.6 45.3 6.1 0.0 4.8

0-3 76.8 65.0 72.1 69.2 100.0 4-7 20.3 35.0 24.3 23.6 0.0

8-10 2.9 0.0 3.6 7.1 0.0

0-3 18.5 1.6 22.3 0.0 56.5 4-7 47.4 11.0 68.0 77.6 34.4

8-10 34.1 87.4 9.7 22.4 9.1

0-3 79.8 60.9 67.8 0.0 56.6 4-7 14.5 31.8 11.4 77.6 34.4

8-10 6.7 7.3 20.7 22.4 9.0



28Tendency to stick feet out of bed at night (Sulph)

29 Tendency to anal itching (Sulph)

30 Quivering or trembling (Gels)

31 Eyelids heavy or drooping (Gels')

32 Headaches radiating from occiput to frontal area (Gels)

33 Feel generally tired or depleted (Gels)

0-3 55.5 27.2 64.4 65.3 65.2 4-7 21.5 18.4 26.7 17.8 23.8

8-10 23.0 54.4 8.7 16.9 11.0

0-3 81.8 77.0 810 85.4 84.1 4-7 16.1 23.0 19.0 4.9 15.9

8-10 2.1 0.0 0.0 9.7 0.0

0-3 55.2 0.0 87.7 55.0 89.8 4-7 35.4 67.5 12.3 45.0 10.2

8 10 10.5 32.5 0.0 0.0 0.0

0-3 49.4 6.1 62.3 69.4 53.6 4-7 40.1 61.4 30.2 30.6 41.3

8 10 10.5 32.5 7.5 0.0 5.1

0-3 61.9 21.8 79.0 77.1 66.6 4-7 30.0 68.6 16.1 16.2 21.5

8-10 8.1 10.6 3.9 6.7 11.9

0-3 33.8 0.0 45.7 36.1 61.1 4-7 42.2 52.3 54.3 32.3 22.5

8-10 24.0 47.7 0.0 31.6 16.4

TABLE 3. Characteristics of pure types based on Homoeopathic Screening Questionnaire (%). Each item is representative of one of more of the following: Ars, Lyc, Gels, Arg-n, Sulph. Figures indicate % of instances in which each item appears for each pure type within the range of scores given (i.e. 0-3, 4~ , 8 10, etc.).


Sex Male 39.9 21.3 61.5 32. l 38.2 Female 60.6 78.6 38.5 67.9 61.8

Age

Diagnosis

20-29 3.9 16.7 0.0 0.0 0.0 30-39 33.8 23.0 78.1 0.0 0.0 40-49 40.1 28.5 19.2 77.0 29.5 50-69 22.2 31.8 2.7 23.0 32.5

Depression/dysthymia 29.9 14.2 21.4 33.6 49.8 Obsessive-compulsive disorder 9.6 5.5 0.0 21.0 12.8 Panic disorder 15.3 16.0 18.2 20.9 6.4 PTSD 5.7 9.2 0.0 14.8 0.0 Social phobia 39.5 55.0 60.3 9.7 30.8

TABLE 4. External characteristics of each pure type (%)

for appo in tmen t s (Arg-n) and a genera l fear o f meeting p e o p l e (Arg-n, Gels) o c c u r r e d more often. Impu l s iveness (Arg-n) was a feature o f th is pure type . The re w a s a g rea te r i nc idence o f a t e n d e n c y to s t ick feet out o f bed (Sulph). Trembl ing , heavy fee l ings in the eyel ids and genera l t i r edness (all Gels) also cha rac te r i zed pure type 1. In summary , this

g r o u p l o a d e d h i g h e s t o n t h e m a j o r i t y o f symptoms , wi th some ex t reme mani fes ta t ions o f the Ars type , a long w i t h Gels and s o m e charac te r i s t ics o f the o ther three med ic ine s . External var iables indicate that pure type 1 is found primarily in w o m e n with a preponderant d i agnos i s o f social p h o b i a and spans across the full age range.


Pure type 2 is characterized by a general lack of anxiety regarding health, death and security. It is generally less fear prone. With respec t to phys ica l cha rac te r i s t i c s and behaviours, it is more likely to desire salt (Arg-n) and notice adverse reactions to eating sweet foods (Arg-n), but overall is a notice- ably stable group from the point of view of a lmos t all cha rac te r i s t i c s in the scale. External variables for pure type 2 indicate it to be a predominantly male group between ages of 30 and 39, carrying a diagnosis of social phobia in 60% of cases.

Pure type 3 is characterized by a preference for hot drinks (Ars, Lyc), desire for salty foods (Arg-n), to be more afraid of heights (Arg-n, Sulph) and of cancer (Ars). They report themselves as generally being con- cemed for other people (Arg-n), suggestible (Arg-n) and reported the highest incidence of extreme fears of jumping from a high place even when not suicidal (Arg-n). They also reported the highest incidence of bad reactions after eating sweet foods (Arg-n). A tendency towards anal pruritus (Sulph) occurred most frequently in this group but this was an uncommon feature in the entire sample. External validators indicated that pure type 3 was predominantly female in the 40 to 69 age group, with a low incidence of social phobia, but a mixed picture of other anxiety disorders and some depression.

Pure type 4 is characterized by absence of serious health concerns, fears of death, insecurity and suggestibility. Panic attacks are rare. Relative to the other groups it is less likely to report stage fright, fear of heights and cancer. There was a tendency towards extroversion (Arg-n) and the type was characterized by good self confidence (Sulph), a hot nature (Sulph), the highest preference for cold drinks among all pure types (Sulph). They were less likely to report diurnal variation in well-being, and were more likely to feel really good on awakening than any other group. Physical characteris t ics o f (Gels) (trembling, heaviness, headaches and tired- ness) were infrequent. External variables for pure type 4 indicated this group to be female, above age 30 and to exhibit depression most commonly and social phobia in some cases.

Discussion A homoeopathic screening questionnaire was

used to assess the extent to which traditional homoeopathic beliefs may hold true in a statistical or classificatory sense. These beliefs are the result of clinical experience gathered over a period of 100 years, which was largely consolidated during the period between 1855 and 1880. Such impressions naturally had been gathered from a broad population, con- vering all ages, ethnic and national groups, different disorders and a significant number of normal volunteers. To do true empirical j~ustice, one would need to test these features m a large and equally heterogeneous population. Our report must be considered no more than a tentative start, without losing sight of its limitations. Thus it would be remarkable if strong confirmation had been obtained, assuming that such confirmation is possible. Equally, lack of clear relationships on the basis of one study does not necessarily dis- confirm the beliefs. With these caveats in mind, we offer some interpretations of the data which, in our opinion, support the view expressed elsewhere that homoeopathy and psychiatry have much in common. 6

Of the four types, extreme Ars features tended to concentrate in pure type 1 and were rarely found in the other types, thus giving some credence to the notion of an Ars drug picture. However, pure type 1 also contained a number of typical Gels, Lyc and Arg-n features; Sulph was mainly absent in pure type 1.

Pure type 2 contained few of the five medicines, suggesting that at least one group in this population emerged with absence of extreme manifestations of the five medicines. Mild manifestations of Arg-n were observed.

Several Arg-n characteristics were found in pure type 3, which contained few features of the other medicines. Pure type 4 incorpo- rated more Sulph features than the other pure types, with few of the other medicine characteristics being found, except that we judged extroversion to be an Arg-n feature.

Diagnostically, social phobia was rare in pure type 3, the most se lec t ive ly Arg-n group. Depressive disorders were most common in pure type 4, which had more Sulph features and few Ars, Lyc or Gels features, suggesting some variabil i ty in diagnostic types for the different medicines. Social phobia was particularly common in pure types 1 and 2, of which one was predominantly male and the other predominantly female.


One test o f the drug picture beliefs is whether or not individual items go together, forming a pattern. Thus all Gels features were most prominent in pure type 1, rather than being scattered at random across different groups. The same was true for Ars. It was interesting to note that the characteristic Lyc diurnal mood variation (worst 3.00 to 5.00 p.m. and > 7.00 to 9.00 p.m.) went with another Lyc feature, bloating after food, in a number of cases, in line with the homoeopathic characterization of this medicine.

Our findings provide qualified support for differences in the drug pictures according to tradit ional homoeopath ic teaching. Thus there was support for the distinctions made between Ars, Arg-n and Sulph. One group, however, showed many of these features. These results show an interesting partial correspondence to the cluster analysis undertak- en by Ives 7 on 111 healthy subjects with regard to Sulphur, Pulsatilla, Lycopodium, Nux vomica, Phosphorus and Sepia. Four clusters emerged, corresponding to Sulphur, Pulsatilla, Sepia and none of the others. Ives noted one cluster to suggest high neuroticism and another stability: the same could be said of our pure types 1 and 4, respectively. Ives's study differed from ours in that external validation included experienced homoeopaths ' judgement as to the importance of each drug feature. In our study, the chosen internal validators were based upon such a judgement but we have not sought additional external confirmation from other homoeopaths.

One implication is that whereas we are sometimes prone to make statements such as 'he is a Sulphur type', or 'she is a Pulsatilla type', in only about 10% of cases was a person found to belong entirely to one of the pure types. More commonly people showed features of more than one medicine. Further investigations on the base rates of pure medicine types in the population, as well as rates of each medicine keynote, and of how different medicines assort with one another would be useful. We are planning such studies with an expanded form of the HSQ.

GoM is a useful technique both for the purposes of medical classification and for relating different medical types to particular treatment outcomes. 3,4 This technique, and other similar multivariate procedures, could be profitably used to explore the questions raised by our study, using larger and more diverse groups of individuals, and a homoeopathic screening questionnaire that covers a wider range of medicines. Multivariate techniques such as GoM have much to offer in the study of homoeopathy, and in turn, could lead to a better appreciation of how homoeopathy may relate to contemporary medical diagnoses. In particular, these techniques may provide us with information about ways in which medicine features can cluster, and ways in which medicine types may assort. For instance, pure type 1 in this study sug- gests that Ars and Lyc features may be highly associated. It is also an intriguing possibility to consider that homoeopathic phenomenolo- gy may reveal differences which correspond to some contemporary psychiatric diagnoses.

References 1 Spitzer RL, Will iams JBW, Gibbon M, First MB.

Structured Clinical Interview for DSM-111-R. Washington DC: American Psychiatric Press 1990.

2 Woodbury MA, Manton KG. A new procedure for analysis of medical classification. Meth lnfo Med 1982; 21: 210-20.

3 Davidson JRT, Woodbury MA, Pelton S, Krishnan KRR. A study of depressive typologies using grade of membership analysis. P~ycholMed 1988; 18: 179-89.

4 Davidson JRT, Woodbury MA, Zisook S, Giller EL. Classification of depression by grade of membership: a confirmation study. P~ychol Med 1989; 19: 98748.

5 Manton KG, Woodbury MA, Tolley HD. Statistical Applications Using Fuzzy Sets. pp. 1 301. New York: John Wiley 1994.

6 Davidson JRT. Psychiatry and homoeopathy: Basis for a dialogue. Br Hom J 1994; 83:78 83.

7 Ives WG. An empirical validation of the homoeopathic theory of type. Proc 35th Congr Liga Medica Homoeopath lnternationalis 1982, 148~il.

Acknowledgement is made to a grant from the Boiron Research Foundation.

Address for correspondence Jonathan Davidson, MD Duke University Medical Center Box 3812, Durham, NC 27710, USA

Multivariate analysis of five homoeopathic medicines in a psychiatric population

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