comorbidity in the anxiety disorders: the use of a life-chart approach

~ ) Pergamon

0022-3956(95)00014-3

J pw~hiat. Res., Vol. 29, No. 6, pp. 467 480, 1995 Copyright @ 1996 Elsevier Science Ltd

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C O M O R B I D I T Y I N T H E A N X I E T Y D I S O R D E R S :

T H E U S E O F A L I F E - C H A R T A P P R O A C H

CAROLINE HUNT and GAVIN ANDREWS

Clinical Research Unit for Anxiety Disorders, School of Psychiatry, UNSW at St Vincent's Hospital, 299 Forbes Street, Darlinghurst, Sydney, NSW 2010, Australia

(Received 26 October 1994; ret:ised 20 March 1995: accepted 28 March 1995)

Summary--Findings of comorbidity across the anxiety and depressive disorders have implications for aetiology, diagnosis and treatment. This paper describes a method to assess one aspect of the relationship between comorbid disorders: the degree to which one illness experience is believed to be caused by the earlier experience of a different illness. The life-chart method involves the use of a semi-structured interview to document the lifetime course of disorders. The method was reliable in a sample of patients treated at a specialized treatment unit for anxiety disorders. Patients fell into three major groupings: those with one disorder only (19%); those who fulfilled criteria for two or more disorders, but with one disorder primary and other disorders secondary to it (55%); and those who fulfilled criteria for two or more independent disorders (26%).

Introduction

Since the advent of operationalized diagnostic criteria for psychiatric disorders there has been growing interest in the phenomenon of comorbidity. Within individuals, comorbidity can be broadly defined as the joint occurrence of two or more disorders over a specified period of time, most often reported as in the lifetime to date. Thus comorbidity as it is currently used refers specifically to the development of disorders over a person's lifetime and not to conditions that temporally co-occur. Comorbidity may be (1) due to the independent occurrence of disorders (this would be consistent with the lifetime risks for each disorder); (2) due to the experience of one disorder acting as a stressor that predisposed to, or somehow caused, the secondary disorder; or (3) due to disorders being independent, influenced by underlying predisposing or causal factors (in which case the increased risks would be general and proportionate to the vulnerability factors). In real life it seems that all three mechanisms may be operative. This paper is about the second mechanism, that is the extent to which one illness experience seemed causally related to a further experience of a different illness. It will be argued that comorbidity has important implications both for clinical research and practice, particularly as current classification systems and diagnostic practice have helped to determine significant comorbidity among psychiatric disorders (Frances et al., 1990).

Our own studies of comorbidity of anxiety and depressive disorders among a large

Correspondence to: Caroline Hunt, M. Psych, Clinical Research Unit for Anxiety Disorders, School of Psychiatry, UNSW at St Vincent's Hospital, 299 Forbes Street, Darlinghurst, Sydney, NSW 2010, Australia.

467

468 c. Hunt and G. Andrews

community sample of twins (n = 892) and patients receiving treatment for panic disorder/agoraphobia (n - 165) found that reports of more than one lifetime diagnosis were four times more frequent than would be expected from the prevalence of the individual diagnoses, while single disorders were correspondingly infrequent (Andrews et al., 1990b). Numerous reports have confirmed high levels ofcomorbidity among anxiety and depressive disorders (e.g. Brown & Barlow,1992; Lepine et al., 1993; Scheibe & Albus, 1992; Schneier et al., 1992; Starcevic et al., 1992). The considerable interest in comorbidity among anxiety disorders and depression has been primarily driven by research that has attempted to delineate the different disorders, validate current diagnostic systems, or uncover the nature and cause of the different disorders. For example, a recent study by Noyes et al. (1992) used findings of different patterns of comorbidity in panic disorder and generalized anxiety disorder to help support the contention that they are distinct and separate disorders. However, research into the nature, predisposing and causal factors, and treatment response of various disorders can be seriously affected by comorbidity with other disorders. As having a single anxiety disorder appears to be the exception rather than the rule, research on the average clinic patient that extends beyond the current symptom picture could be at risk of describing factors that are associated with the comorbid disorders, or with anxiety or depressive disorders in general, rather than factors specific to the disorder in question.

The study of the relationship between comorbid disorders may well increase our under- standing of the nature of the disorders. For example, three studies with longitudinal comorbidity data have defined depressive and anxiety disorders as primary or secondary on the basis of their temporal relationship (Angst et al., 1990; Cloninger et al., 1990; Hagnell & Grasbeck, 1990). The results of all three reports suggest that individuals with primary remitted depression were less likely to have a secondary anxiety disorder relative to the likelihood that individuals with primary anxiety disorders would have a secondary depressive disorder. These studies also suggest that secondary depression in individuals with anxiety disorders occurs after many years of chronic anxiety. The implications of such findings include the likelihood that the high degree of comorbidity between depressive and anxiety disorders may not reflect a common aetiology, for if they shared the same aetiology, a symmetry in risk would be expected (Cloninger et al., 1990). Therefore, the high levels of comorbidity between anxiety and depressive disorder may well reflect the chronicity of the anxiety disorders in the clinical samples studied, although the quasi population twin study by Andrews et al. (1990b) also found such comorbidity.

In practice, clinicians are required to make a different type of primary-secondary distinction. They make judgements about the syndrome that is predominant when making choices about treatment, or when assessing the impact of comorbid disorders on prognosis. In addition, they often make judgements about the causal relationship between disorders. Birchwood et al. (1993) have recently addressed the significant occurrence of depression in individuals with chronic schizophrenia. These authors hypothesize that the depression is a psychological response to an apparently uncontrollable life event, namely the illness of schizophrenia and its long-term disabilities. If depression is truly secondary to the experience of this chronic disorder rather than independently determined or intrinsic to the illness itself, then it would always follow the primary disorder and mediating factors such as demoralization or perception of loss of control would be important targets for treatment.

Life-chart Comorbidity Assessment 469

This work provides an example outside the anxiety and depressive disorders of how under- standing the relationship between comorbid disorders can aid clinical practice. Longitudinal comorbidity data for anxiety and depressive disorders suggest that a similar relationship may exist between anxiety disorders and secondary depression. Primary and secondary depressive disorder may well be different, with secondary depression more often a demoralization reaction to chronic impairment rather than a specific comorbid condition requir- ing treatment in its own right.

While it is argued that comorbidity is important both in research and in clinical practice, one of the main difficulties to date has been technical problems in its assessment. Structured diagnostic interviews have been the main source of diagnostic information in studies of comorbidity. They offer a reliable and systematic method of making psychiatric diagnoses free of the influences that characterize clinical interviews, influences that include the use of hierarchical notions of diagnosis and the need for parsimonious formulations. For example, the Schedule for Affective Disorders and Schizophrenia (Spitzer & Endicott, 1978) was one of the first structured diagnostic interviews to ask about the age of onset of episodes and to require the interviewer to make a distinction on the basis of this age of onset information between primary depression and depression that is secondary to another disorder. However, most structured interviews do not gather the additional detailed information necessary for the assessment of comorbidity, such as information regarding the course of symptoms over time and the clustering of episodes of different disorders (Burke et al., 1991). It is also difficult to know whether it is best to determine onset to be at the first occurrence of a symptom, when groups of symptoms appear, or at the first point in time at which all criteria required for a diagnosis have been met. If structured diagnostic interviews were to collect such information, and they could, it is likely that the necessary increase in length would severely limit their practicality.

Assessments of comorbidity are not immune from the usual problems of reliability of retrospective reports (Rogler et al., 1992). Perhaps not surprisingly, such temporal assessments have questionable reliability. Using a version of the Diagnostic Interview Schedule, Wittchen et al. (1989) found relatively low test-retest agreement (53-70%) over 1-2 days for the age at onset questions concerning the phobias, generalized anxiety disorder and episodes of major depression when a + 1 year range was considered to be agreement. Moras & Barlow (1992) reported 58 % test-retest agreement for the exact onset of a disorder using the ADIS with a kappa of 0.23 over a mean interval of 16 days. The ADIS is a semi- structured diagnostic interview for the anxiety disorders with otherwise excellent reliability. These results of lessened reliability of temporal information about onset may in part reflect the nature of the anxiety and depressive disorders, which tend to be slow and insidious in their onset and which may come and go over time.

Structured interviews also appear unable to distinguish between a primary disorder and secondary and independent co-existing disorders in the same way that a clinician might. Hence they appear unable to answer questions of causal inference or symptom pre- dominance which require a degree of clinical judgment (Klerman, 1990). In the anxiety disorders the relationship between panic disorder with agoraphobia and social phobia provides a good case in point. Both disorders can be characterized by persistent, regular panic attacks, debilitating anticipatory anxiety, and avoidance of similar situations. In the


absence of clear temporal precedence it may be difficult to determine whether the diagnosis of panic disorder has arisen because of acute anxiety in social situations where the individual has been exposed to scrutiny, whether avoidance of situations is due to the fear of panic and its consequences, or whether the two diagnoses have been determined independently.

With these difficulties in mind, attempts have been made to improve the assessment of comorbidity. Wittchen (1992) has developed a Comorbidity Module for the Composite International Diagnostic Interview (Wittchen et al., 1991). This module involves a second stage interview with questions generated from information gathered in the core structured interview. In this second interview detailed information is sought about the onset, peaks and sequences of symptoms, syndromes and diagnoses and their relationship to some other variables. A computerized scoring algorithm generates the second stage interview in a matter~ of minutes, and preliminary results suggest that the variables can be determined with acceptable reliability. It was also noted by Wittchen that the heavy reliance on retrospective reporting weakens reliability, and therefore cognitive probes were incor- porated into the method. The cognitive probe strategy attempts to link the occurrence of psychopathology with other events or circumstances in an individual's life that may be remembered more accurately than concepts or symptoms of the psychopathology. A similar practice has also been reported with the use of a 1-year time line for mapping symptoms in children assessed by the Diagnostic Interview Schedule for Children (reported by Burke et al., 1990) and also in a method for the assessment of alcohol consumption in which drinking behaviour is linked to memorable events across a specified period of time (Miller, 1991). It remains to be seen whether more detailed information from a structured interview will allow the often subtle discrimination necessary for determining the relationship between comorbid diagnoses.

The aim of the present study is to investigate the feasibility of a life-chart method to explicate the nature of comorbidity and to present preliminary findings and reliability data from the use of this method. The question asked is whether two disorders are independent and require independent treatment and reflect an independent aetiology, or whether one disorder is secondary to the other, and treatment and aetiology are related to the primary or core disorder. In this life-chart method, a patient's illness history is mapped out using information from a first-step structured interview, the CID1. The method documents the life-time course of a patient's disorders against significant life events and enables the temporal relationship between multiple diagnoses to be determined, and then, whether the disorders are perceived as independent or secondary to each other.

Methods

Development of the life-chart method

The life-chart method was developed for a research project investigating the aetiology of specific anxiety disorders in which the co-occurrence of other disorders would represent a problem in the search for disorder-related aetiological factors. As with the Comorbidity Module developed by Wittchen, the administration of a structured diagnostic interview is


used to elicit the information required. In the current paper, the life-chart approach uses information that is generated from the results of the computerized version of the Composite International Diagnostic Interview, the CIDI-Auto (Peters et al., 1994; WHO, 1993).

The CIDI-Auto. The Composite International Diagnostic Interview (CIDI) is a comprehensive, fully structured diagnostic interview which provides, by means of computerized algorithms, current and lifetime diagnoses according to the criteria of ICD-10 and DSM- III-R. The CIDI procedure also allows the determination of age at onset, age at most recent occurrence, as well as some selected information about the course of the disorder. It produces consistent (i.e. reliable) diagnoses across raters and time (Andrews et al., 1995; Wittchen et al., 1991, 1994). The CIDI-Auto is the WHO approved computerized version of the CID1 and faithfully reproduces the questions in the standard paper-and-pencil interview. The CIDI-Auto has acceptable validity when compared to a LEAD standard diagnosis (Peters & Andrews, 1995). A test retest reliability study and a comparison between the CIDI-Auto and the paper-and-pencil CIDI are currently being undertaken (Peters et al., 1994). CIDI-Auto can either be administered by an interviewer or completed by the respondent directly. A report is generated with the diagnostic information required, and with symptoms reported, and severity, onset and recency information.

The life-chart method involves the use of a semi-structured interview in which subjects are asked to help the interviewer to plot their illness history and other significant information and events on a longitudinal chart. Information from the CIDI about life-time diagnoses and the diagnostic criteria fulfilled in meeting those diagnoses is available to the interviewer and provides the basis for the illness history that is plotted on the chart. The method was used by the authors of the current paper in a long-term follow-up of depression (Kiloh et al., 1988; Andrews et al., 1990a) and a similar technique has been described in the Longitudinal Interval Follow-up Evaluation (LIFE) (Keller et al., 1987).

The interview begins by charting a number of personal details. The subject's age, living arrangements, educational and occupational milestones, and other significant life events (e.g. marriage, births of children, divorce) are plotted for each 6 months of the subject's adolescent and adult life. This process aims to establish significant points in the course of an individual's life and to provide reasonably valid anchor points to which diagnostic information can be linked. Using the relevant CIDI-Auto information each positive diagnosis is then sequentially plotted on the chart. In each instance, onset and recency information is then checked against that reported from the ClDl-Auto, and discrepancies are resolved with the subject. In cases where subjects have more than one ClDI-Auto diagnosis the subject is asked about the relationship between each diagnosis on the chart. This questioning occurs after all diagnoses have been individually documented and aims to determine whether a diagnosis (1) exists independently of other diagnoses, or (2) is secondary, or appears to be entirely explainable in terms of the limitations placed on the subject by another disorder.

Once the relationship between disorders has been elicited and coded, subjects are finally asked if there have been any significant problems, treatments, or other life events that have not been coded so far in the interview. A written manual and coding sheet have been developed to standardize the administration of the life-chart and to increase reliability, and these are available upon request from the authors. A section of the coding sheet has been

472 C. H u n t and G. Andrews

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A C A L L G I D T I 1

E O A E I F F D R L p E E E U A R A N C P P E L T E E A P H H S D C V V

Y H T W A O O S R O C E E E A O I O G N B B O I U H A N N A G M O R A I I I C O G O R T T R E E N K D C A A D N S L E S S

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Add earlier history on tile next page if needed .L

Figure 1. Sample o f coding sheet from the life-chart approach.

L I f E

E V E N T S COMMENTS

Write comments on back of page,

reproduced in Fig. 1, and segments from the manual containing specific questions used in the life-chart approach are reproduced in Table 1.

Subjects

The life-chart was administered to 100 consecutive patients who attended out-patient treatment programmes for their primary disorder at a tertiary referral clinic for anxiety disorders. The primary clinical diagnoses of the sample were panic disorder without agoraphobia (n = 9), panic disorder with agoraphobia (n = 37), social phobia (n = 36), or obsessive-compulsive disorder (n = 18), Patients were excluded from treatment if they met criteria for a psychotic disorder, an organic disorder or for an affective disorder which was deemed to require immediate treatment. The mode of referral to the clinic and the low drop-out rate are described in detail elsewhere (Hunt & Andrews, 1992).The patient sample comprised 57 females and 43 males, and their mean age was 35 years (SD = 10.1),

Nineteen additional patients provided test-retest data for the life-chart method. These

Life-chart Comorbidity Assessment

Table 1 Samples of Specific Questions used in the Administration of the Life-chart Approach

473

"'The aim of this exercise is to get an overall picture of some of the problems that you have been experiencing, some of the events that have occurred in your life, and the circumstances surrounding these problems and events. Here is a chart on which I would like to record some of these things.'"

Code subject's current age and a number of other ages on the life-chart. Use Coding Key to record information for 'home' ,

Ask: "Where are you living at the moment?" "How long have you been living there'?" "'When did you stop living with your parents?'" etc.

" 'When did you leave school'?" "Have you done any further study?" etc.

"Are you working at the moment?" "How long have you been doing that'?" etc.

(If married) "When were you married?" (If children) "When were your children born?" etc.

Ask for each positive CIDI diagnosis: "Can you remember the questions you answered on the computer? You said that you had experienced times when you [list relevant criteria.fi~r disorder, including frequency and severity criteria].""

"Could you tell me when you first remember this group of problems occurring? In other words, when you first experienced [disorder]?"

"'When was the last time'?"

"'Between the first time and the last time, have you ever had a year when you were free of [key symptoms]? What was happening then? Why do you believe that you were not troubled during that time?"

"'Did any thing happen at the time when the [disorder] began that you believe may have caused the [disorder] in some way'?" (Record if life events or explanation of onset are reported).

Following the coding of all positive CIDI diagnoses: "You have indicated that you have experienced [list disorders]. Can you say which one you believe is the most important?"

"Some people say they have [disorder A] because they have [disorder B]. Others might say that if one of these disorders would go, so would the other. Which is true in your case?"

patients also attended out-patient treatment programmes at the clinic, and their primary treatment diagnoses were panic disorder with agoraphobia (n = 13) and social phobia (n = 6). This sample comprised 12 females and seven males, and their mean age was 38 years ( S D = 10.0).


Procedure

Each subject attended an appointment prior to commencing treatment at which the structured diagnostic interview and life-chart assessments took place. In the current study, subjects completed the respondent-administered form of the anxiety disorder and depression sections of the CIDI-Auto (Version 1.0). CIDI-Auto responses were combined using the WHO scoring program for DSM-III-R diagnoses (Version 1.0, November 1990). Immedi- ately after DSM-III-R diagnoses and other relevant information from the CIDI-Auto had been scored and a report generated, the life-chart was administered. All assessments were completed within the same day. The DSM-III-R diagnoses of interest in this study were panic disorder with and without agoraphobia, social phobia, obsessive-compulsive disorder, generalized anxiety disorder, major depressive disorder, and dysthymia.

The life-chart was administered to an additional 19 patients on separate occasions by two investigators blind to each others' results. The first assessment was conducted in a manner identical to the larger sample. The life-chart was readministered on a second occasion using the CIDI-Auto results from the first assessment. The test-retest intervals ranged between 2 days and 2 weeks, over which time the majority of subjects had com- menced treatment.

Results

Subjects in the main study (N = 100) were assigned to one of three groups on the basis of their life-chart findings: (1) only one positive CIDI-Auto diagnosis (PURE group); (2) two or more positive CIDI-Auto diagnoses, but all diagnoses judged to be secondary to a primary (or CORE) diagnosis (CORE group); or (3) two or more independent positive CIDI-Auto diagnoses (MIXED group). In the CORE group, the life-chart results provide information about the potential causal relationship between diagnoses and therefore allow a comparison between the life-chart and CIDI-Auto-derived patterns of comorbidity. The primary secondary relationship between diagnoses for members of the CORE group (rated using the life-chart method) was checked against the age of onset of each diagnosis rated in the CIDI-Auto. Of the 86 pairs of diagnoses in the CORE group, 26 pairs of diagnoses were each rated with CIDI-Auto as having the onset of each diagnosis within the same year. Therefore, while the CIDI-Auto was unable to provide information about a temporal or causal relationship between disorders, the life-chart method did provide such information. In a further 42 pairs there was agreement between the CIDI-Auto and the life- chart method, in that the disorder designated to be primary by the life-chart method had an earlier age of onset according to the CIDI-Auto. There was disagreement between the CIDI-Auto and life-chart method in the remaining 18 pairs of diagnoses (or 21% of the primary diagnoses) in that the diagnosis designated as secondary was identified as having an earlier age of onset by the CIDI-Auto. Nine (50%) of the disagreements concerned the diagnoses of panic disorder and social phobia, seven (39%) concerned depression and a phobic disorder, while the remaining two disagreements concerned generalized anxiety disorder and a phobic disorder.

The differences in time between the onset of the core disorder and the onset of the secondary disorder were obtained from both the life-chart and the CID1-Auto results for


84 of the 86 pairs of diagnoses in the CORE group. The time differences for each of the two methods were highly correlated (r = .89, p < .001). A t-test for paired samples indicated that there was no significant difference between the mean time difference found by the life- chart method (x = 19.9 months, s = 78.7) and by the CID1-Auto (x = 22.9 months, SD = 87.5; t = -0 .72, d f = 83, p > .4). While the subjects in the PURE and MIXED groups could not provide information in respect to the potential causal relationship between diagnoses, age of onset information was compared between the two methods for each positive CIDI-Auto diagnosis. Full age of onset information was available for 73 of the 76 diagnoses across the PURE and M I X E D groups. The age of onset for the CIDI-Auto and life-chart was highly correlated (r = .82, p < .001) and a t-test for paired samples indicated that there was no significant difference between age of onset as assessed by the CIDI-Auto (x = 25.5 years, s = 11.4) and age of onset as assessed by the life-chart (x = 24.2 years, s = 11.0; t = -1 .61 , dl'= 72, p > .1),

How reliable was the life-chart procedure? The test-retest agreement for allocation to the groups in the reliability sample (N = 19) was acceptable, with a kappa of 0.75 (Table 2). Three subjects were allocated to different groups on the basis of their two life-chart assessments. The discrepancies involved one rater concluding that diagnoses were independent, while the other rater concluded for one subject that social phobia was secondary to generalized anxiety disorder, for a second subject that panic disorder with agoraphobia was secondary to social phobia, and for a third subject that social phobia was secondary to panic disorder with agoraphobia. Perfect agreement between the two raters in regard to the temporal relationship between each subject's CIDI-Auto diagnoses was achieved in 16 of the 19 cases (84%).

Table 3 shows the number of subjects with PURE, CORE or M I X E D diagnoses in the main sample (N = 100) by their treatment diagnosis. Nineteen per cent of the sample received only one positive CIDI-Auto diagnosis. Fifty-five per cent of cases indicated that all additional diagnoses were secondary to a primary diagnosis, and of these, five subjects indicated that their perceived primary diagnoses were not consistent with the focus of current treatment. Three of the 36 subjects accepted for treatment for social phobia believed that their social phobia was secondary to panic disorder (two without and one with agoraphobia) and one subject reported that their social phobia was secondary to an obsessive-compulsive disorder. One of the 46 subjects accepted for treatment for panic disorder with agoraphobia believed that their anxiety had begun secondary to a depressive

Table 2 Reliability Samph, (N = 19): Allocation to Groups by Independent raters

Rater 2 Pure Core Mixed

Rater 1 Pure 4 0 0 Core 0 8 1 Mixed 0 2 4

Pure, Only one CIDI-Auto diagnosis; Core, more than one CIDI- Auto diagnosis, but all diagnoses secondary to CORE diagnosis; Mixed, more than one independent CIDI-Auto diagnosis.

476 C. Hunt and G. Andrews

Table 3 Main Sample (N = 100): Life-chart Groupings by Primary Treatment Diagnosis

Treatment diagnosis n PURE CORE MIXED

Panic disorder without agoraphobia 9 2 7 0 (22%) (78%)

Panic disorder with agoraphobia 37 8 15 14 (22%) (40%) (38%)

Social phobia 36 5 24 7 (14%) (67%) (19%)

Obsessive~compulsive disorder 18 4 9 5 (22%) (50%) (28%)

Total 100 19 55 26

See legend for Table 2.

disorder. Twenty-six per cent of the sample indicated that they had independent comorbid disorders. The probability of assignment to these three groups (PURE, CORE or MIXED) was not associated with the focus of current treatment (chi square = 8.96, df= 6, p > 0.2).

The primary and secondary diagnoses of subjects assigned to the CORE diagnostic group are shown in Table 4. The most common secondary diagnoses were major depression (61%) and panic disorder with agoraphobia (55%). The least common secondary diagnosis was obsessive-compulsive disorder, with only one subject reporting that this CIDI-Auto diag-

Table 4 Secondary Diagnoses for Patients in CORE Group

CORE diagnosis

Secondary diagnosis Panic Panic

disorder disorder Obsessive Generalized without with Social compulsive anxiety Major

agoraphobia agoraphobia phobia disorder disorder depression Dysthymia

Panic disorder without agoraphobia

Panic disorder with agoraphobia

Social phobia

Obsessive- compulsive disorder

Major depression

Totals

8 - - - - 4 0 1 6 1 (50%) (12%) (75%) (12%)

16 8 1 4 9 0 (50%) (6%) (25%) (56%)

20 4 13 0 2 13 1 (20%) (65%) (10%) (65%) (5%)

10 4 3 2 - - 3 5 0 (40%) (30%) (20%) (30%) (50%)

1 0 1 1 0 0 ---

55 (25%) (55%) (43%) (2%) (18%) (61%) (4%)

Row percentages are greater than 1 O0 owing to multiple secondary diagnoses.

Life-chart Comorbidity Assessment

Table 5 Summary, of Pairs of lndependent Diaynosis jor Patients in MIXED 9roup (N = 26)

477

Generalized Social Obsessive-compulsive anxiety Major phobia disorder disorder depression Dysthymia

Panic disorder without agoraphobia 0

Panic disorder with agoraphobia 7

Social phobia

Obsessive -compulsive disorder 2

0 0 0 0

0 0 3 0

2 0 2 3

0 3 0

Four subjects are not included in Table 5 as they had more than the two independent CIDI-Auto diagnoses shown above. The independent diagnoses for these four subjects were: (1) panic disorder with agoraphobia, generalized anxiety disorder, and major depression; (2) panic disorder with agoraphobia, social phobia, and generalized anxiety disorder; (3) panic disorder with agoraphobia, social phobia, generalized anxiety disorder, and major depression; (4) panic disorder with agoraphobia, social phobia and obsessive~zompulsive disorder.

nosis was secondary to their primary diagnosis (panic disorder). Independent comorbid diagnoses for subjects assigned to the MIXED group are shown in Table 5.

Discussion

The life-chart method may prove to be an important procedure for establishing the relationship between diagnoses derived from structured diagnostic interviews. The method appears to produce consistent results when administered by independent raters on separate occasions. To aid reliability, there is a real attempt to anchor symptoms to significant events, activities and situations in an individual's life which may be remembered with greater accuracy. There is evidence that individuals can increase their accuracy of recall with the use of partial temporal information to reconstruct the event's date (Thompson et al., 1993). Partial temporal information can include recalled event sequences, recalled relationship, schooling or work landmarks or boundaries, or some other tag related to an event.

The procedure also has reasonable face validity as both patients and interviewers find it logical and acceptable. It appears to be a reasonably straightforward task for patients to describe the course of their disorders in terms of exacerbations and remission along a longitudinal chart. In addition, the method appears to overcome one of the critical issues in the study of comorbidity in regard to the most appropriate measurement of the onset and course of a disorder. While an assessment of chronological sequence has obvious implications for the causal relationship between disorders, the results of the life-chart method do not rely solely on temporal information. For example, in many cases where the CIDI-Auto was unable to provide information about a potential causal relationship between disorders because the two onsets were reported to have occurred within the same year, the life-chart approach obtained information from patients which specified a causal relationship.

The comparison between the life-chart findings and the CIDI-Auto age of onset questions will in part reflect the reliability of the CIDI-Auto age of onset findings and in part


reflect the reliability of the life-chart. Clear agreement between the initial CIDI-Auto onset information and the life-chart was found in only 50% of the CORE group. However, the comparison of onset-related information for both the CORE, and PURE and MIXED samples suggests a high degree of consistency. As the accuracy of temporal information from retrospective interviews is questionable, these findings should be interpreted cautiously. The 21% of pairs of diagnoses in which the two methods disagreed may well reflect inaccuracy in the reporting of age of onset in disorders which have slow and insidious onsets and which share similar symptom profiles. This is certainly the case for the disagreements in the test- retest data. It is interesting that none of the discrepancies in the larger sample involved the diagnosis of obsessive-compulsive disorder which is arguably phenomenologically more distinct from the other disorders of interest. It is also worth noting that in 17 of the 18 cases of disagreement, the life-chart result was in agreement with the findings of the initial clinical interview in which the treatment diagnosis was determined and suggest that, if anything, the mode of ascertainment of age of onset in the CIDI-Auto needs to be reviewed. Further research is required to understand fully the reason for the discrepancies between temporal information from the CIDI-Auto and the conclusions of the life-chart. For example, the collection of additional corroborating information, such as from significant others, may help to assess the validity of the life-chart approach.

Further investigations using the life-chart method are currently underway. For instance, the method may well add to the procedural validity of the CIDI (the extent to which the instrument yields results similar to another established diagnostic procedure). A recent study assessed the procedural validity of CIDI-Auto diagnoses against a LEAD standard (Spitzer, 1983) in a similar sample of patients to those described in the present study (Peters & Andrews, 1995). This study found that, across the diagnoses of interest, agreement between the two procedures was acceptable, ranging from 68% in panic disorder to 98% in obsessive-compulsive disorder. With the exception of generalized anxiety disorder and obsessive-compulsive disorder, the CIDI-Auto tended to make more diagnoses than the LEAD standard. It is possible that the difference between the two diagnostic procedures could be accounted for by the number of secondary diagnoses made by the CIDI-Auto which were excluded by clinicians who were, for example, able to determine that a patient's panic attacks were primarily due to their fear of negative evaluation in situations where they were exposed to scrutiny. In the current sample, while only 5% of subjects reported a primary diagnosis that was not consistent with their treatment diagnosis, neither the subject nor the interviewer was blind to the treatment diagnosis assigned prior to completion of the life-chart.

The life-chart method's ability to predict treatment response in comorbid diagnoses will provide a test of its own validity. One would predict that if core disorders are successfully treated, disorders reported as secondary would also resolve without the need for further specific treatment. However, the course of truly independent diagnoses would be less likely to have a temporal relationship with the CORE diagnosis, despite the probable generalization of treatment effects across the anxiety disorders.

While findings from the sample described should not be analysed in great depth without further validation of the life-chart method, they do provide some interest. For example, previous findings of comorbidity in the literature may need to be reassessed in the light of


the large number of diagnoses deemed to be secondary. The data presented in the current study suggest that 70% of patients with a diagnosis of panic disorder, social phobia and obsessive-compulsive disorder have only one diagnosis--the treatment diagnosis. The presence of independent diagnoses, particularly depression and social phobia, have implications for the addition of therapeutic interventions that will target these disorders. The implications for treatment of the anxiety disorders in the light of empirical and theoretical aspects ofcomorbidity have been discussed elsewhere in detail (Andrews, 1995, 1996; Brown & Barlow, 1992).

In conclusion, these preliminary findings suggest that the life-chart is a method worthy of further investigation. There is to date no other procedure with established validity for the assessment of comorbidity among psychiatric disorders. The procedure of following a structured diagnostic interview with a detailed analysis of the relationship between disorders may provide a reliable and valid aid to the study of comorbidity in anxiety and depression. It is also likely that the method will be equally useful when applied to the study of comorbidity across other psychiatric disorders.

Acknowledgements The authors would like to thank Drs Hans-Ulrich Wittchen and Lorna Peters for their helpful comments to earlier drafts of this paper.

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comorbidity in the anxiety disorders: the use of a life-chart approach

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