Prevalence of Generalized Anxiety Disorder in General Practice in Denmark, Finland, Norway, and Sweden

Generalized anxiety disorder is frequent in European and North American populations. The two large epidemiological studies performed in the United States—the Epidemiologic Catchment Area Study ( 1 ), which used DSM-III, and the National Comorbidity Study ( 2 ), which used DSM-III-R —showed lifetime prevalence rates of generalized anxiety disorder as being 3.1 and 3.8 percent, respectively. A study from Oslo, Norway, reported a 12-month prevalence rate for generalized anxiety disorder of 1.9 percent and a lifetime prevalence rate of 4.5 percent ( 3 ). A recent study from six European countries found a 2.8 percent lifetime prevalence rate of generalized anxiety disorder and a 1.0 percent 12-month prevalence rate ( 4 ). All studies reported higher prevalence rates among women. Lieb and colleagues ( 5 ) summarized 27 studies and reported a 12-month prevalence rate of 2 percent in the adult population. In a recently published National Comorbidity Survey Replication study, Kessler and coworkers ( 6 ) found the 12-month rate of generalized anxiety disorder to be 3.1 percent, almost identical to the 12-month prevalence rate given in the National Comorbidity Study ten years earlier ( 2 ).

A large proportion of patients with generalized anxiety disorder are seen by general practitioners. Wittchen and colleagues ( 7 ) found that 5.3 percent of patients in Germany (point prevalence) who saw a general practitioner fulfilled the criteria for having a DSM-IV generalized anxiety disorder. A World Health Organization (WHO) study of general practitioners in 15 countries by Üstün and Sartorius ( 8 ) showed an average six-month prevalence rate of 7.9 percent for ICD-10 generalized anxiety disorder. Using data from this study, a separate analysis from five major cities in Europe showed that the 12-month prevalence rates of generalized anxiety disorder (without comorbid depression) varied significantly: Berlin, 7.3 percent; Paris, 7.2 percent; Mainz, 4.5 percent; Manchester, 3.0 percent; and Groningen, 1.5 percent; the overall rate was 4.8 percent ( 9 ). The European part of the WHO study showed that only half of the cases of generalized anxiety disorder were recognized by the general practitioner ( 9 ).

In an editorial, Lang and Stein ( 10 ) argued for "improved identification and management of anxious state in primary care settings." They pointed to the frequent occurrence of anxiety disorders in primary care, the underrecognition of such disorders by primary care providers, and the "negative outcomes, including reduced physical and emotional functioning and quality of life … and increased healthcare costs." However there is a considerable body of literature showing that training courses for general practitioners do not improve their ability to identify common mental disorders ( 11 , 12 , 13 ).

Recent literature points to opportunities for improving anxiety disorder treatment results ( 14 ). However, to gain these benefits, general practitioners must be able to recognize the disorders among patients.

The health care systems in the countries represented in this study are as an overall principle organized in three parts: primary health care, secondary health care (provided in hospitals, in other inpatient facilities, and by private practicing specialists), and the social welfare system. General practitioners function as first-line physicians, as gatekeepers for the secondary health care systems. With few exceptions, patients cannot consult secondary health care without a referral note from the general practitioner. Aftercare following medical treatment (for example, surgery, acute myocardial infarction inpatient treatment, and inpatient psychosis treatment) is the responsibility of the social welfare system, which collaborates with general practitioners in order to cover medical and social needs.

The average number of patients seen per day by each general practitioner in Scandinavia is 15 to 20, which is substantially lower than the average of 60 patients per day, for example, in Germany.

In the Nordic systems, expenses for health care are paid through taxes. Secondary health care is financed by fixed annual budgets; general practitioners (and practicing specialists) are paid per services rendered through the government municipalities or regional authorities, which means that the patient does not have to pay for health care visits. Although some of the Nordic countries may charge a low fee for primary or secondary health care, most of the Nordic countries provide free health care.

Despite the expression "private practicing physician," such physicians in the Nordic system are employed by the government or counties, meaning they are strictly regulated as to, for example, limited annual income and fixed prices for services, with variation from country to country.

This study explored the point prevalence rate of generalized anxiety disorder and major depression among patients who saw participating general practitioners in Denmark, Finland, Norway, and Sweden on preselected target days. The study also investigated the rate of co-occurring major depression among patients with generalized anxiety disorder, determined the proportion of cases of generalized anxiety disorder that were recognized by the general practitioners, and investigated factors associated with recognition.

Methods

Procedure

The study was cross-sectional and was carried out in general practices in Denmark, Finland, Norway, and Sweden in September 2001. The study follows the design and methods used in a previous German study ( 7 )—that is, both studies gathered information about general practitioners when they agreed to participate (prestudy), both studies gathered data from patients' self-ratings on one of three consecutive days (September 16, 17, or 18, 2001, in our study), and both studies gathered information about the patients' physical and mental conditions from a questionnaire filled in by general practitioners. Informed consent was not required by the countries for this type of study.

In the questionnaire about their patients, the general practitioners were asked whether the patients had generalized anxiety disorder, other anxiety disorders, a major depressive episode, or other mental disorders. They were also asked whether the patients had any physical illnesses.

Questionnaires were collected and sealed nationally, and transported to the Max Planck Institute in Munich for data entry and preliminary analyses.

In Denmark a total of 3,500 general practitioners were informed about the study and invited to participate, and 450 answered in the affirmative. The 450 interested general practitioners were contacted by project monitors, who informed the practitioners about the details of the project. The project monitors from all four countries were trained and instructed during a joint meeting by the principal investigator (PM-J), one of the authors (H-UW), and Yvonne Copeland, licensed nurse (employed by Wyeth). Among the Danish general practitioners, 302 decided to take part in the study. The participating Danish general practitioners were then instructed in detail about the questionnaires by the project monitors, and they filled in a prestudy questionnaire about their education, experiences, number of patients seen per day, attitude toward psychopharmacologic treatment, and so on. Then each participating general practitioner asked patients to participate in the project during one of the days mentioned above.

In Sweden 152 general practitioners were invited to participate, and 141 gave a positive response; 131 participated. (Swedish data have previously been published in a national journal [15].) In Finland 103 general practitioners were invited by the project monitors, and 90 gave a positive response; 82 participated and were instructed by the monitors.

The procedure described for Denmark was followed by Sweden and Finland. Norway did not have any project monitors and the information and instructions to the participating general practitioners were given in writing by the Norwegian project leader (AAD). The written information to the Norwegian participating general practitioners contained the same information that was given to the Danish, Swedish, and Finnish participating general practitioners by the monitors—that is, information about the background and purpose of the study and instructions for filling out the survey. In Norway 141 general practitioners were included in the prestudy, and 133 participated.

Patient sample

Patients aged 16 years or older (18 years or older in Denmark) who consulted their general practitioner on a survey day were asked to participate.

Instruments

The questionnaires were translated into Danish from a German version of a similar study ( 7 ). This translation created the background for the Norwegian and Swedish versions. Danish, Swedish, and Norwegian are closely related languages that are read and understood across the countries. The Finnish procedure for translating was similar to the Danish procedure. The national translations were back-translated into German by a different translator. One of the authors (H-UW), who is affiliated with the Max Planck Institute, approved the German back-translations.

The patients' self-rating questionnaire assessed DSM-IV diagnostic criteria for generalized anxiety disorder—as measured by the 20-item Generalized Anxiety Questionnaire (GAS-Q) ( 16 )—and major depressive episode—as measured by the 11-item Depression Screening Questionnaire (DSQ) ( 16 )—as well as questions about previous physical and mental illnesses.

Psychiatric classification systems like DSM-IV and ICD-10 are based on the presence or absence of operationalized diagnostic criteria. When structured interviews are used to examine such criteria, the diagnostic reliability is improved considerably. Questionnaires by which the patients rate themselves on the diagnostic criteria have been developed for various mental disorders. The patient-rated instruments in this study (GAS-Q and DSQ) are both criteria-based questionnaires.

In the study presented here the patients filled in the GAS-Q and DSQ scales; the ratings were electronically analyzed to determine whether each patient met DSM-IV criteria for generalized anxiety disorder and major depressive episode. These diagnoses were not further validated in this study, but the self-rating method has been thoroughly validated previously as summarized below.

The GAS-Q is a modification of the Anxiety Screening Questionnaire ( 17 ), which was developed to diagnose general anxiety disorder according to DSM-IV criteria ( 18 ). The GAS-Q consists of 20 items that are answered only if the first question is scored positive: "During the past 4 weeks, have you been bothered by feeling worried, tense or anxious most of the time?" (Criterion A of general anxiety disorder in DSM-IV .) Two items screen for panic disorder and agoraphobia, and they were not considered for this study. Test-retest reliability of the GAS-Q over a two-day retest period showed a kappa value of .74 for the general anxiety disorder diagnosis. Congruent validity comparing GAS-Q diagnosis with the DSM-IV algorithm for general anxiety disorder of the Composite International Diagnostic Interview showed a kappa of .72 ( 16 ).

The DSQ was developed for the diagnosis of a major depressive episode according to DSM-IV criteria and is based on self-rating ( 19 ). The DSQ consists of 11 criteria-based items that are rated on a 3-point scale. Consistent with the DSM-IV criteria cutoff value, a diagnosis of major depressive episode was assigned when at least five of the items were rated as positive. In the German part of the European study, the internal consistency of the DSQ showed a Cronbach's coefficient alpha of .83 ( 20 ). Test-retest reliability over a two-day period found a kappa value of .82 for major depressive episode. Tests of the DSQ diagnosis versus a diagnosis based on a structured diagnostic interview found a kappa of .89 ( 21 ).

Patients' diagnostic status and the severity of general anxiety disorder and major depressive episode were rated with the Clinical Global Impression-Severity Scale (CGI-S) ( 22 ), a standardized assessment tool widely used as an outcome measure in psychiatric research ( 16 ). The CGI-S has the following wording: "In your clinical judgment how severely does this patient suffer from major depression/general anxiety disorder?" The ratings are 1, not ill at all; 2, a borderline case; 3, only mildly ill; 4, moderately ill; 5, seriously ill; and 6, extremely seriously ill.

Statistical procedures

The age-standardized rates (with 95 percent confidence intervals [CIs]) of generalized anxiety disorder and major depressive episode were calculated on the basis of GAS-Q and DSQ scores. Stratification on country and clustering by physician used procedures for survey estimation in the Stata software system, and the total sample (both genders from all countries) was used as the standard population. Differences between countries and genders were compared in two-by-two tables of age-adjusted counts by chi square tests.

The proportion of generalized anxiety disorder cases recognized by general practitioners was calculated for each country and for the total sample. Variables associated with recognition of generalized anxiety disorder cases as defined by the GAS-Q were explored by using logistic regression analyses stratified on country and clustered by physician. The variables, which were characteristics of the general practitioners and of the patients, were included as independent variables both with a univariate and with a stepwise backward elimination procedure. Data were analyzed by using Stata version 8.2 ( 23 ). A significance level of 5 percent and two-tailed tests were applied.

Ethics

In Norway the Committee of Medical Ethics (Region East) approved the study. In Sweden the Research Ethics Committee of the Karolinska Institutet approved the study. The Danish Ethical Committees system approved the Danish part of the study. The ethical committee of Päijät-Häme Central Hospital District approved the Finnish protocol.

The national Wyeth AB subsidiaries financed the study and managed the logistics of the study in each country. The project monitors instructed the general practitioners and collected the questionnaires. The project monitors were not allowed in any way to promote the interests of the company during the study—for example, they were not allowed to mention the company's products or carry badges. Wyeth AB was not involved in data analyses, which were done preliminarily at the Max Planck Institute, Munich, and done further by the biostatistician (LF) in collaboration with the principal investigator. Also, Wyeth AB was not involved in writing or approving the manuscript.

Results

From Denmark 4,543 patients participated (2,901 females, or 64 percent, and 1,642 males, or 36 percent). From Norway 1,764 patients participated (1,125 females, or 64 percent, and 639 males, or 36 percent). From Sweden 1,348 patients participated (852 females, or 63 percent, and 496 males, or 37 percent). From Finland 1,224 patients participated (743 females, or 61 percent, and 481 males, or 39 percent). Overall, the study had 8,879 participants (5,621 females, or 63 percent, and 3,258 males, or 37 percent). No information on race or ethnicity is available, but the average Scandinavian population is approximately 95 percent Caucasian.

The mean±SD age of the total sample was 48.6±18.1 years, ranging from 46.3±15.8 years in Finland to 52.6± 18.5 years in Sweden. Among the 471 patients with generalized anxiety disorder, the mean age was 41.8±14.1 years, ranging from 40.0±12.3 years in Finland to 42.7±15.0 years in Denmark.

The prevalence rates of generalized anxiety disorder are shown in Table 1 . The overall age-standardized rates were 4.8 percent for males and 6.0 percent for females. Comparisons between countries show no statistical differences among males. In Norway the prevalence rate of 3.7 percent for females was significantly lower than that found in the other countries.

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Table 2 shows the prevalence rates of major depressive episode. Standardized rates ranged between 7.2 percent in Sweden and 11.5 percent in Denmark for males and between 9.9 percent in Norway and 14.2 percent in Denmark for females. For both genders the Danish rates were significantly higher than those found in Norway; for males, the Danish rates were significantly higher than those found in Sweden.

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Table 3 shows that rates of co-occurring generalized anxiety disorder and major depressive episode varied for males (between 1.8 percent in Sweden and 2.8 percent in Finland) and for females (between 1.6 percent in Norway and 3.5 percent in Finland); 93 percent of the cases were valid (no missing data) and were included in the calculations. Again, the rate of co-occurring major depressive disorder for females was significantly lower in Norway than in other countries.

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Because of exclusions resulting from missing information, the figures for the total numbers of participants vary in Tables 1 , 2 , and 3 .

Table 4 shows the proportion of cases of generalized anxiety disorder diagnoses based on the patients' self-rating on the GAS-Q that were recognized by the general practitioners. The proportion was higher in Norway than in the other countries.

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Table 5 shows the results of univariate analyses of variables as predictors of recognition of generalized anxiety disorder. The variables shown in the table all met the following criteria for univariate correlation with general practitioners' recognition: odds ratio (OR)≤.5 or OR≥2.0 or p≤.15. Also included in the analysis were age and gender. These variables were all included in a stepwise backward elimination logistic regression analysis of predictors of recognition of generalized anxiety disorder by general practitioners.

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The reference standard for generalized anxiety disorder was patients' self-rating on the GAS-Q. If patients had formerly been given a diagnosis of generalized anxiety disorder or anxiety neurosis or if they presented with anxiety symptoms, general practitioners were significantly more likely to recognize generalized anxiety disorder. If patients presented with physical complaints, the likelihood was significantly decreased. It is noteworthy that comorbid major depression did not improve the recognition of generalized anxiety disorder.

Discussion

The study presented here used a design that was comparable to that used in a recent German study by Wittchen and colleagues ( 7 ), and when our study stratified on country and clustered by physician (taking into account the correlation among patients seeing the same doctor), the two studies had similar prevalence rates of generalized anxiety disorder. The German study found a rate of generalized anxiety disorder of 5.3 percent overall, whereas our study found rates of 4.8 percent for males and 6.0 percent for females. Our study found rates of generalized anxiety disorder and co-occurring major depressive disorder that were approximately twice those found in the German study. However, it is well known that there is a great variability of prevalence rates for co-occurring mental disorders (for example, from 2.9 to 10 percent), as reported by Lang and Stein ( 10 ).

Overall, it can be concluded that the prevalence rates of generalized anxiety disorder and major depression in different European countries, including Denmark, Finland, Norway, and Sweden, are as high as those found in the United States.

Two findings should be emphasized: first, the prevalence rate of generalized anxiety disorder is not negligible among patients who see general practitioners, and second, a high proportion of the generalized anxiety cases were not recognized by the general practitioners—24 to 44 percent as summarized by Lang and Stein in their editorial ( 10 ), and 37 percent in the study presented here.

For at least two or three decades, general practitioners' recognition of nonpsychotic mental disorders has been extensively surveyed and discussed. However, despite these efforts, our study and other ones found no general increase in the proportion of nonpsychotic mental disorders recognized by general practitioners. Factors that seem to influence the recognition of these disorders among general practitioners in our study are previous diagnoses and the patient's report of anxiety symptoms. Participation in training courses and interest among general practitioners in generalized anxiety disorder did not seem to improve identification, and comorbidity of major depression did not have any effect on the identification of generalized anxiety disorder.

However, the study presented here shows that the Norwegian results differ from those found in the other countries: in Norway the prevalence of generalized anxiety disorder was lower and the proportion of general practitioners who recognized cases of generalized anxiety disorder was significantly higher. In 1995 Dahl and colleagues ( 24 ) developed the Structured Psychiatric Interview for General Practice (SPIFA). Between 1995 and 2001 more than 2,500 Norwegian general practitioners attended SPIFA courses that mainly taught them to identify anxiety disorders, depression, and suicidality by use of structured questioning, which may explain the higher recognition among the Norwegian general practitioners.

One of the explanatory variables that did not reach significance in our study was whether the physician took at least one course related to anxiety disorders within the past two years; another was whether he or she took at least one course related to depression within the past two years. This contradicts the supposed effect of the Norwegian training program. However, the questionnaire did not obtain information about the length and quality of the courses in question; they may be courses or lectures with minor impact. It can be argued that the questionnaire did not gather enough information about the courses; thus, if the questionnaire measured for the intensity of the course, more intense courses may have been significant in our analyses.

Generalized anxiety disorder and major depressive episode are diagnoses made by psychiatrists; therefore, methods used in the study presented here may be questioned because we used diagnoses that used patients' self-ratings as the gold standard. However, this methodology has been tested several times in various settings: in a Nordic multicenter study ( 25 , 26 ), internationally ( 8 ), and recently in a German study ( 7 ), the latter with a methodology replicated in the study presented here.

The study presented here does not claim to be representative of all general practitioners in the four countries in question. General practitioners are offered an overwhelming number of invitations for meetings, courses, surveys, and research studies that focus on a total of between 30 and 40 medical specialties invited by an unknown number of pharmaceutical companies. It should therefore be assumed that the participating practices represent general practices that have an above average interest in mental disorders. The proportion of practitioners who recognized these disorders in this study ( Table 4 ) may therefore be higher than figures for the average general practitioner. The representativeness of the participating patients could not be measured because of ethical reasons—information on the characteristics of patients who declined to participate could not be gathered and these patients could not be further investigated. In the Swedish part of the study, some of the general practitioners were asked to estimate how many patients chose not to participate in the study, and they gave estimates of 10 to 20 percent.

Conclusions

Our study included a large number of participants across Denmark, Norway, Sweden, and Finland and found that the prevalence rates of generalized anxiety disorder and major depressive episode among patients served by general practitioners were within the same range as those found in other studies. However, our study showed a tendency for higher rates of major depressive episode than those found in other studies. The proportion of cases of generalized anxiety disorder that was recognized by general practitioners was discouragingly low—between one-third and one-half of the cases—and no practically useful associated variables were found, except for formerly diagnosed anxiety disorder and anxiety as a presenting symptom. Also, if a patient who met criteria for having generalized anxiety disorder presented with physical symptoms, the general practitioners were less likely to recognize the disorder. However, a higher proportion of general practitioners in Norway recognized generalized anxiety disorder, perhaps as a result of a nationwide training course offered to more than 2,500 general practitioners, which suggests the usefulness of large focused educational programs.

Acknowledgments

This study was financed by a nonconditional educational grant from Wyeth AB Denmark, Finland, Norway, and Sweden; the grant provided funds mainly for project monitors. The authors thank Sabine Apelt, Dipl.-Psych., for supervising the field work and data entry.