Psychosomatics 49:426-437, September-October 2008
doi: 10.1176/appi.psy.49.5.426
© 2008 Academy of Psychosomatic Medicine
Nonfearful Panic Disorder in Chest-Pain Patients: Status After Nine-Year Follow-Up
Christine B. Bringager, M.D.,
Katrine Gauer, M.D.,
Harald Arnesen, M.D., Ph.D.,
Svein Friis, M.D., Ph.D., and
Toril Dammen, M.D., Ph.D.
Received October 16, 2006; revised December 15, 2006; accepted January 4, 2007. From the Dept. of Psychiatry, Ullevaal University Hospital, 0407 Oslo, Norway; the Medical Faculty, University of Oslo, 0317 Oslo, Norway; the Dept. of Cardiology, Ullevaal University Hospital, 0407 Oslo, Norway; the Faculty Division, Ullevaal University Hospital, University of Oslo, 0318 Oslo, Norway; the Institute of Psychiatry, University of Oslo, 0317 Oslo, Norway; and the Dept. of Behavioural Sciences in Medicine, University of Oslo, 0317 Oslo, Norway. Send correspondence and reprint requests to Christine Bull Bringager, M.D., Dept. of Research and Education, Psychiatric Division, Ullevaal University Hospital, 0407 Oslo, Norway. e-mail: christine.bringager{at}medisin.uio.no
© 2008 The Academy of Psychosomatic Medicine
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ABSTRACT
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BACKGROUND: Nonfearful panic disorder (NFPD) is a type of panic disorder (PD) that was first described in 1987 among cardiology patients who had panic attacks without the experience of fear. NFPD may be considered a subtype of PD with significant impact on the long-term outcome of chest pain patients. OBJECTIVE: The authors sought to explore the long-term outcome of NFPD and PD. METHOD: Authors studied 199 patients previously referred to cardiology outpatient investigation because of chest pain. Assessments comprising cardiological and psychiatric (SCID–I) examinations were conducted after 9 years. RESULTS: At follow-up, no patients suffered from NFPD, but 18% had panic disorder with fear (PD). There were no significant differences between the baseline NFPD (N=11) and PD (N=44) patients regarding psychiatric comorbidity, chest pain, healthcare utilization, and health-related quality of life at follow-up. CONCLUSION: NFPD can have a significant impact on the long-term outcome of chest pain patients even though they may not seek psychiatric treatment.
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INTRODUCTION
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Nonfearful panic disorder (NFPD) is a type of panic disorder (PD) that was first described by Beitman and colleagues in 1987 among cardiology patients who had panic attacks without the experience of fear.1 These patients met the DSM-III–R criteria for PD by reporting attacks of intense discomfort and at least 4 of the 12 remaining symptoms on the screening checklist, but they did not report subjective free-floating anxiety or fear of dying, fear of "going crazy," or doing something uncontrollable (Table 1).
To the best of our knowledge, only four previous studies in cardiology and emergency department settings have estimated the prevalence of NFPD; these found that 22%–44% of PD patients fulfilled the criteria for NFPD.1–4 However, the concept of NFPD is somewhat controversial; it is not a DSM-IV illness, and it remains equivocal whether NFPD is a subgroup of PD or whether it is a distinct diagnostic entity.5 Questions have also been raised as to whether NFPD may be better classified as a somatoform disorder or whether NFPD patients have an undetected medical disorder that is incorrectly identified as NFPD.3,4
Previous studies have concluded that it is reasonable to regard NFPD as a variety of PD, rather than a distinct diagnostic entity, because no significant differences have been found between PD and NFPD patients in terms of demographic characteristics,1,3,4 frequency of panic attacks (except the cognitive symptoms of panic attacks),3 health-related quality of life,4 the prevalence of PD among first-degree relatives,6 response to treatment with anxiolytic medication (imipramine or lorazepam),7 and response to lactate infusions (in neurological patients with PD and NFPD).7 However, some studies have reported lower prevalence of comorbid psychiatric disorders and lower scores on self-reported anxiety and panic/agoraphobia symptoms in NFPD patients.3,4
Longitudinal studies are clinically important because they provide knowledge of the diagnostic stability and long-term outcome of diseases; however, we are aware of only one previous study exploring the course of NFPD. Fleet and colleagues3 conducted a 2-year follow-up study supporting the notion that NFPD is a subgroup of PD because, over the 2-year period, both groups had either not improved or worsened in self-report measures of anxiety, panic, and agoraphobia. There were no significant differences between the groups in the number of chest pain episodes, emergency department visits, hospitalizations, and perceived health status at follow-up.3 Nevertheless, this study suffers from methodological limitations such as lack of diagnostic psychiatric assessments at follow-up, no second cardiological evaluation, and absence of assessment of health-related quality of life, which is considered an important target for treatment. The NFPD patients may have developed fear and thus fulfilled the criteria for PD at follow-up, or they may have developed heart disease or other somatic disorders, which could explain their panic-like symptoms and poor prognosis.
To the best of our knowledge, this is the first long-term follow-up study of NFPD. It was conducted to extend the knowledge of both the concept and clinical outcome of NFPD by rediagnosing the patients 9 years after initial examination and comparing the outcome of PD patients with and without fear. It is, therefore, both an important supplement to the validation of the concept of NFPD, and a source of new knowledge regarding the long-term course of NFPD. From outcome studies of PD in psychiatric settings, we know that PD often has a chronic course, with serious implications regarding functional and social disability8 and quality of life.8,9 If the course of NFPD is similar to that of PD, it would support the concept of NFPD as a subtype of PD and emphasize the need to recognize this group of patients in order to provide treatment.
We have previously published a study of 199 patients consecutively referred to cardiology outpatient clinics because of chest pain,4 in which 17 of the 76 patients (22.4%) suffering from PD met the criteria for NFPD. We now present the 9-year follow-up status of this population so as to 1) estimate the proportion of patients who fulfill the criteria for NFPD and PD at follow-up; and 2) compare the long-term outcome of the patients with NFPD, PD, and No-PD at baseline. We do this with regard to a) comorbid psychiatric disorders; b) self-reported anxiety, agoraphobia, somatization, depression, and chest pain; c) presence of somatic disorders; d) health-related quality of life; and e) healthcare utilization and use of medication.
We hypothesize that the outcome of the NFPD patients will not differ significantly from the outcome of the PD patients and that both will have a worse outcome than the No-PD patients.
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METHOD
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The study was conducted in accordance with the revised Declaration of Helsinki. The research protocol was accepted by the Regional Ethics Committee in November 1994. At the time of the baseline and follow-up investigations, all participants signed informed-consent forms.
Subjects
Baseline
The baseline participants in the study were 199 patients with no previously documented heart disease who were referred for investigation of chest pain to one of four cardiology outpatient clinics in Oslo, Norway, from December 1994 to November 1996. At the first examination, 32 patients (16%) were diagnosed as suffering from coronary artery disease (CAD), and 167 were diagnosed as having non-cardiac chest pain; 76 patients (38%) suffered from PD at initial examination, 17 of whom (22.4%) fulfilled the criteria for NFPD. At baseline, no statistically significant difference in frequency by gender was found among the PD (patients with NFPD excluded), NFPD, and No-PD patients. Women constituted 58%, 65%, and 43% of the groups, respectively. Patients with PD or NFPD did not differ significantly by age (mean [standard deviation; {SD}]: 48.1 [9.2] versus 49.4 [12.9] years, respectively), years of education, or income. Compared with the No-PD patients, both groups were younger (No-PD patients: 52.7 [8.8] years), had fewer years of education, and lower income. A more detailed description of the study population has been published elsewhere.4
Follow-Up
Between 8 and 10 years after the baseline study (mean: 8.6 years; range: 8.1–9.9 years), patients were asked to participate in a follow-up study; 14 patients had died during the follow-up period (4 in the PD and 2 in the NFPD patient group), and 1 patient had suffered a major stroke and was unable to participate. Two of the PD patients died of a cardiovascular cause; the other deaths were from various causes. Of the 184 eligible patients, 150 participated in the follow-up study (82%). Of the 34 nonparticipants, 7 had left the country; 12 could not be located; and 12 patients did not participate for various of the following reasons: study not relevant to their condition at the time (N=4); did not have time (N=4); too difficult to come to the hospital (N=1); afraid of giving away sensitive information (N=1); disappointed with previous treatment at the hospital (N=1); and not known (N=1). Three patients who filled in questionnaires did not attend psychiatric or cardiological evaluation sessions and were considered nonparticipants.
Of the 150 participating patients, 12 attended the psychiatric, but not the cardiological evaluation session, which was scheduled to take place about a week after the psychiatric evaluation session. The reasons for their absence are not known. They were still considered participants because information about their previous cardiac disorders could be obtained from their medical records.
Assessment of Sampling Bias
There were no significant differences between the 150 participants and the 34 nonparticipants with regard to sex, age, years of education, or income at baseline. The participants also did not differ significantly from nonparticipants in the prevalence of CAD (12% versus 17%, respectively), PD (29.3% versus 30.6%, respectively), NFPD (7.3% versus 12.2%, respectively), or any of the outcome measures at baseline.
Procedure
From December 2003 to September 2005, invitations to participate in the follow-up study were mailed to all eligible patients. The invitation included details of an appointment with the first author (a psychiatric resident trained in psychiatric interviewing) and an appointment for cardiological evaluation. Both meetings were located at the outpatient clinic of the Department of Cardiology, Ulleval University Hospital, Norway.
In order to ensure that the evaluations were blinded, the person who performed the psychiatric interview did not know the result of the previous psychiatric evaluation or previous or current cardiac examinations; likewise, the cardiologists were blind to the psychiatric evaluation results.
Study Groups
The number of deaths was obtained from the National Death Registry. We then compared the long-term outcome of the three groups: patients with panic disorder (PD; N=44), patients with nonfearful panic disorder (NFPD; N=11), and patients without panic disorder (No-PD; N=95) at baseline. Patients were diagnosed with PD if they met the criteria for panic disorder by the Structured Clinical Interview for DSM–IV (SCID).10 They were diagnosed with NFPD if they reported having recurrent, unexpected attacks of intense discomfort without reporting fear of dying, "going crazy," or losing control, but at least four of the remaining symptoms of a panic attack according to the criteria described by Beitman et al.1 and adjusted to DSM–IV (Table 1). The No-PD patients met neither the criteria for PD nor NFPD. According to this, throughout the results and discussion sections, the term PD is used exclusively for patients with fearful panic attacks at baseline and NFPD exclusively for patients with nonfearful panic attacks.
Measures
Structured Psychiatric Interview
Psychiatric disorders at baseline and follow-up were assessed with the Structured Clinical Interview for DSM–IV (SCID–I)10 by the last author at baseline and by the first author at follow-up. The SCID–I is a semistructured clinical interview that yields current and lifetime psychiatric diagnoses (Axis I disorders). For the purpose of this study, we recorded PD and NFPD as current (diagnostic criteria met 1 month before the interview) or historical (including PD in partial and complete remission), major depression as current or historical, and the other diagnoses as current. The diagnoses were recorded immediately after the interviews. All interviews were audiotaped, and 32 randomly selected tapes were rated by an experienced psychiatrist blinded to the diagnoses. The interrater reliability scores were estimated for the diagnoses of PD, major depression, generalized anxiety disorder, and somatoform pain disorder. The interrater reliability scores ranged from acceptable to excellent for all psychiatric diagnoses at both baseline and follow-up ( : 0.69–1.0).
Self-Report Measures
The following questionnaires were used at both baseline and follow-up: 1) questionnaire on demographic characteristics, including sex, age, and work status; 2) a chest pain questionnaire, including persistence of chest pain symptoms and use of healthcare facilities and medication; and 3) the Symptom Checklist-90–Revised (SCL–90–R),11 which measured psychological distress (we limited our analyses to the Anxiety, Somatization, and Depression subscales; 4) the Agoraphobic Cognitions Questionnaire (ACQ) and the Mobility Inventory for Agoraphobia (MIA), which measures panic/agoraphobia symptomatology;12 5) the Short-Form McGill Pain Questionnaire (SF-MPQ), applied to assess quality and intensity of chest pain;13 and 6) health-related quality of life, assessed with the Medical Outcome Studies Short Form–36 (SF–36),14 which consists of eight subscales: Physical Functioning, Role Limitation due to reduced Physical Functioning, General Health, Vitality, Body Pain, Social Functioning, Mental Health, and Role Limitation due to Emotional Problems. A psychometrically sound and validated Norwegian translation of the SF–36 was used in the present study.15,16 The internal consistency was high for all scales (Cronbach  : 0.74–0.93).
Cardiological Assessments and Registration of Somatic Disorders
Follow-up evaluations of the study patients were conducted by four cardiologists, one of whom also took part in the baseline study. A cardiological assessment form was completed by the cardiologist for each patient. The form recorded data on the patients’ previous or prevailing medical diseases and current medication. In all patients, a standard bicycle ergometer test was performed at baseline and follow-up according to the procedure described by Nordenfelt et al.17 The classification criteria and procedure for this test are reported in more detail elsewhere.18 If inconclusive, the test was classified as such, and the patient was referred for further tests, such as thallium scintigraphy or coronary angiography. A cardiologist not participating in the cardiological assessment evaluated and approved all cardiological diagnoses before the final analyses. The classification criteria and procedure for this test are reported in more detail elsewhere.18
Statistical Analyses
Comparisons between the PD, NFPD, and No-PD patients were performed by chi-square test for dichotomous variables. When an overall difference was found with p<0.10, we continued with between-group analyses. The independent Student’s t-test was used for normally distributed continuous variables, and the Mann-Whitney U test was used for continuous variables with non-normal distributions. Distributions were visualized with histograms. All tests were two-tailed. Paired-sample t-tests were used to estimate change in scores of continuous variables from baseline to follow-up for each of the three study groups; we applied a significance level of 0.05. Agreement between interviewers on psychiatric diagnoses was assessed with the kappa coefficient. The SPSS/PC 12.0 Statistical Package was used for all data analyses. (Because of missing data, N may differ for some of the variables.)
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RESULTS
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Prevalence of Panic Disorder and Nonfearful Panic Disorder at Follow-Up
The results are shown in Table 2. Of the patients with current PD at baseline, 27% still suffered from current PD at follow-up, whereas 34% reported a history of PD symptoms. Of the patients with NFPD at baseline, 18% had current PD at follow-up, and 45% reported a history of PD symptoms. No patients fulfilled the criteria for current or historical NFPD at follow-up.
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TABLE 2. Prevalence of Current and Historical Panic Disorder (PD) and Nonfearful PD at Follow-Up in Patients Meeting Criteria for PD, Nonfearful PD, or No-PD at Baseline, N (%)
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Comparison of Patient Groups
Comorbid Axis I Disorders at Follow-Up
The results are shown in Table 3. There was no significant difference in the prevalence of agoraphobia and anxiety disorders among the study groups. NFPD patients had a significantly higher prevalence of any somatoform disorder, as compared with No-PD patients. The prevalence of current major depression was significantly higher among PD than No-PD patients, and there was a nonsignificant trend (p=0.051) toward a higher prevalence of history of major depression among the NFPD, as compared with No-PD patients. There was no significant difference in prevalence of any specific psychiatric disorder between the PD and NFPD patients; however, whereas 76.3% of the PD patients had any comorbid psychiatric disorder, prevalence in NFPD patients was 54.5% (p=0.089). No patients suffered from psychotic or bipolar disorders.
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TABLE 3. Comorbid Axis I Disorders at Follow-Up in Patients Diagnosed at Baseline With Panic Disorder (PD), Nonfearful PD, or No-PD, N (%)
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Self-Reported Anxiety, Depression, and Somatization at Follow-Up
Table 4 shows the patients’ self-report measures of anxiety, depression, and somatization.
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TABLE 4. Self-Reported Symptoms of Anxiety, Somatization, Depression, Agoraphobia, and Chest Pain at Follow-Up in Patients With Panic Disorder (PD), Nonfearful PD, and No-PD at Baseline, Mean (Standard Deviation)
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On the SCL–90 Anxiety subscale and Agoraphobic Cognitions Questionnaire, PD patients scored significantly higher at follow-up than both NFPD and No-PD patients, and there was no significant difference between the two latter groups. Both PD and NFPD patients had improved from baseline; they had significantly lower SCL–90 Anxiety scores at follow-up.
On the SCL–90 Somatization subscale, the PD patients scored significantly higher than No-PD patients; otherwise, there was no significant difference among the study groups. All three groups had lower scores at follow-up than at baseline, but the change was statistically significant only for the NFPD and No-PD patients.
On the SCL–90 Depression subscale, the PD patients also scored significantly higher than the two other groups at follow-up, whereas there was no significant difference between the NFPD and No-PD patients. All groups had experienced a small but nonsignificant improvement from baseline to follow-up.
Chest Pain at Follow-Up
Chest pain in the last month was reported by 65.9% of PD patients, 54.5% of NFPD patients, and 53.7% of No-PD patients, resulting in no significant differences among groups (p=0.392). Of the 86 patients who had experienced chest pain in the preceding month, PD patients reported significantly more intense pain than the No-PD patients, and the level of pain in the NFPD patients was between the two other groups for all MPQ scales (Table 4). Regarding the total pain intensity, as measured by a visual-analog scale, NFPD patients had the highest score, although this was not statistically significant from the other groups.
Somatic Disorders at Follow-Up
As seen in Table 5, PD patients reported a significantly higher prevalence of dyspepsia and peptic ulcer than the No-PD patients, and NFPD patients reported a significantly higher prevalence of peptic ulcer and hypothyroidism than No-PD patients. There was no significant difference in prevalence of somatic disorders between PD and NFPD patients, although the mean number of somatic disorders was slightly higher in the PD group.
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TABLE 5. Somatic Disorders at Follow-Up in Patients Diagnosed at Baseline with Panic Disorder (PD), Nonfearful PD, or No-PD, N (%)
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Health-Related Quality of Life at Follow-Up
The quality-of-life results are presented in Table 6. PD patients scored significantly lower than No-PD patients (a higher score indicates better health) on all subscales of the SF–36 at follow-up. The scores of the NFPD patients did not differ significantly from those of PD patients, and although the NFPD patients scored lower than the No-PD patients on seven of eight subscales, the differences reached statistical significance for the Physical Functioning, Body Pain, and General Health subscales only. There was no significant change in SF–36 scores for any of the groups from baseline to follow-up.
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TABLE 6. Comparison of Mean (Standard Deviation) Short-Form–36 (Quality of Life) Scores at Follow-Up for Patients With Panic Disorder (PD), Nonfearful PD, and No-PD at Baseline
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Healthcare Utilization Last Year
A greater proportion of PD and NFPD patients reported seeking medical help for chest pain symptoms (25% and 27% versus 15%) and for other symptoms (84% and 91% versus 77%) than patients without PD; these differences, however, did not reach statistical significance. Although the finding did not reach statistical significance, a greater proportion of the NFPD patients had consulted the emergency department (NFPD: 27%, PD: 18%, and No-PD: 12%), general practitioner (NFPD: 82%, PD: 64%, and No-PD: 64%), and medical specialist (NFPD: 46%, PD: 39%, and No-PD: 39%) during the last year. The mean number of medical consultations was significantly greater in NFPD than in No-PD patients (7.5 [7.8] versus 3.5 [5.1]; p=0.05), whereas there was no significant difference in the number of consultations between NFPD and PD patients (5.3 [6.9]). Also, there were no significant differences among the three groups regarding the number of patients who had consulted a psychiatrist during the last year (PD: 4.5%, NFPD: 9.1%, No-PD: 7.4%).
Current Use of Medication
No significant difference between the three study groups was found regarding the use of antidepressants or anxiolytics. The proportion of PD, NFPD, and No-PD patients using antidepressants was 10%, 9%, and 7%, respectively, whereas, for anxiolytics, it was 17%, 9%, and 11%, respectively. However, NFPD patients reported a significantly greater use of analgesics than both PD (45% versus 17%; p=0.042) and No-PD patients (45% versus 18%; p=0.029).
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DISCUSSION
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The present study is the first to explore the diagnostic stability of NFPD and long-term outcome of NFPD patients. The main finding of this study was that whereas 17 of 76 PD patients met the criteria for NFPD at baseline, none of the 11 patients who participated in the follow-up interview were diagnosed with NFPD 9 years later; also, of the 11 NFPD patients who participated in the follow-up interview, 7 patients (64%) reported either current PD or a history of PD with fear. Interestingly, 17 (39%) of the PD and four (36%) of the NFPD patients did not fulfill the criteria for any panic disorder at follow-up. We believe this may be explained by the instability of recall, as has previously been reported in patients with somatization disorder19 and depression.20
These findings suggest that, after 9 years, the PD and NFPD patients are almost indistinguishable; the majority of the NFPD patients have experienced both fearful and non-fearful panic episodes during the course of their illness. They support the study of Rachman and colleagues,21 who found that, for several panic trials, patients could be divided into three groups: one group reporting exclusively panic attacks with fear, one group reporting exclusively panic attacks without fear, and one group reporting both fearful and non-fearful panic attacks. The participants in our study were diagnosed as having either panic attacks with or without fear, exclusively, based on the last month of attacks; this categorization assumes that this period was representative, although it may not have been. A second evaluation of the NFPD patients may have revealed more anxiety in conjunction with panic attacks than was found in the first examination.
One must also consider whether NFPD patients really did have panic attacks without fear at baseline, or whether they denied their emotional symptoms unconsciously or because of shame or fear of stigma associated with psychiatric disorders. Alexithymia has also been suggested as an explanation to their lack of fear; however, in a previous report, we found no significant difference in self-reported alexithymia between PD and NFPD patients.4 Moreover, NFPD patients may have been concerned that their physical symptoms would be minimized and under-investigated if they admitted cognitive or emotional symptoms. This is in line with the finding that only 31% of the patients with PD or NFPD wanted a report with information about panic disorder and treatment options to be sent to their general practitioner after their first psychiatric evaluation. The most commonly stated reason for not experiencing a treatment need at baseline was a primary need for clarification of their cardiovascular illness.18
Undetected medical or somatoform disorders have been suggested as causes of NFPD symptoms. The results of the psychiatric diagnostic reevaluation confirm the notion of NFPD as a subgroup of PD, rather than a distinct diagnostic entity. Furthermore, given that there was no significant difference between the PD and NFPD patients regarding the prevalence of any cardiological or other somatic disease, it seems unlikely that an undetected medical disorder was the cause of symptoms in NFPD patients at baseline. In fact, the number of medical disorders was highest among the PD patients. The cardiological investigation revealed that seven (17.5%) of the PD and two (22.2%) of the NFPD patients had CAD, and 32 PD patients (84.2%) and five NFPD patients (83.3%) had any medical disorder at follow-up. A limitation of the study was that no effort was made to identify cases in which chest pain at baseline proved to be organic in origin. Therefore, we cannot firmly conclude that NFPD symptoms at baseline were not caused by an undetected medical disorder, but the fact that most NFPD patients fulfilled criteria for PD with fear some time during follow-up suggests that this was not the only explanation. There is a well-known association between PD and various medical disorders, and the symptoms caused by these disorders may serve as internal cues that initiate panic attacks in vulnerable persons.22
There was no significant difference in the prevalence of somatoform disorders between the PD and NFPD patients: 11 (25%) of the PD and 4 (36%), of the NFPD patients suffered from a somatoform disorder. If NFPD were better explained by the diagnosis of somatoform disorder, one would expect a greater overlap of the diagnoses. However, the rates of both medical and somatoform disorders were high for both PD and NFPD patients, and it is difficult to know with certainty whether the reported medical conditions were actual diseases or somatoform symptoms. Apart from the cardiological investigation, these disorders were not verified by thorough medical examination, but rather, recorded by a cardiologist. Thus, the patients may have reported symptoms they perceived as somatic disorders; for instance, breathing problems explained as asthma, or chest pain explained as dyspepsia or peptic ulcer, when the symptoms may not have been of organic origin. A high prevalence of unexplained physical symptoms is common in patients with anxiety disorders.23 A high comorbidity between panic disorder and gastrointestinal disorders, as well as asthma, has also been reported.23 The symptoms caused by these disorders may serve as internal cues that initiate panic attacks in vulnerable persons.23
Moreover, we hypothesized that the outcome of the PD and NFPD patients would not differ significantly and that both groups would have a worse outcome than the No-PD patients. This hypothesis was only partially confirmed; the PD patients had significantly higher scores than the NFPD patients regarding the symptoms of panic and agoraphobia, whereas there was no significant difference between PD and NFPD patients regarding the development of comorbid psychiatric disorders, persistence of chest pain episodes, healthcare utilization, and self-reported health-related quality of life.
Previous studies have reported a lower prevalence of agoraphobia in NFPD than in PD patients3,4,24 and a lower prevalence of generalized anxiety disorder in NFPD patients.3 After 9 years, there were no significant differences in prevalence of any comorbid anxiety disorders between the two groups. The rates of generalized anxiety disorder and specific phobia had increased in both groups, as compared with baseline, and the prevalence of agoraphobia had decreased from 46% to 14% in PD patients from baseline to follow-up, most likely because only 27% of them suffered from current panic attacks at follow-up. Although 18% of NFPD patients suffered from current PD with fear at follow-up, an additional 45% reported a history of PD with fear, and there were similar rates of anxiety disorders in PD and NFPD patients. This did not seem to affect their experience, or at least their report, of typical panic symptoms. However, regarding the self-reported symptoms of panic and agoraphobia, both the PD and NFPD patients had improved at follow-up. The PD patients, however, still had significantly higher scores than NFPD patients, who had scores no different from the No-PD patients both at baseline and follow-up. Anti-panic treatment (i.e., serotonin reuptake inhibitors and high-potency benzodiazepines) may have improved these symptoms, but we did not collect systematic data regarding the treatment that they may have received during the follow-up period because we believed there would be recall difficulties. However, during the last year, 21% of the PD and 9% of NFPD patients had received such medical treatment. Interestingly, this was also the case for 17% of the No-PD patients.
Regarding health-related quality of life, the outcome of the PD and NFPD patients did not differ significantly, and they both had a worse outcome than the No-PD patients. All groups were unchanged from baseline to follow-up, and the outcome of the PD and NFPD patients did not differ significantly, whereas they both had a worse outcome than the No-PD patients. This is an important finding, because improvement in health-related quality of life is one of the targets in the treatment of PD.25 The outcome of the NFPD patients was especially poor as compared with No-PD patients regarding the subscales constituting the Physical component of the SF–36 scale; this could not be explained by a difference in the number of medical diseases between the groups. In fact, the scores of the NFPD patients did not differ significantly from, or were worse than what is reported in patients with chronic stable angina,26 symptomatic angina,27 patients with CAD before surgery,28 patients with PD,9 and patients with other chronic disorders.9 These findings add to the evidence that NFPD patients are particularly distressed by physical impairment and pain and that this distress is unchanged after 9 years.
Anti-panic treatment (i.e., serotonin reuptake inhibitors and high-potency benzodiazepines) may have modified psychological distress and quality of life in PD and NFPD patients, but we did not collect systematic data regarding the treatment they may have received during the follow-up period because we expected there would be recall difficulties. However, during the previous year, 21% of the PD and 9% of NFPD patients had received such medical treatment. Interestingly, this was also the case for 17% of the No-PD patients. The physical impairment and pain reported by NFPD patients was also reflected in their use of analgesics, which was significantly higher than in the two other groups, as well as a more frequent use of the healthcare system by NFPD, as compared with No-PD patients.
There is little empirical evidence for the effective treatment of NFPD. To the best of our knowledge, there is only one small study that examined the treatment of NFPD patients, wherein PD and NFPD patients responded similarly to anti-panic medication.7 Cognitive therapy may also be effective, given that it is one of the treatments of choice in PD,31 and it has also been found to be effective in patients with medically unexplained physical symptoms.32 Although cognitive therapy of PD is focused on modifying the patients’ catastrophic interpretations of bodily sensations,33 we speculate that this model may be less suitable in NFPD patients, who report less cognitive distortion. A model focusing on stress management, activity regulation, emotional awareness, cognitive restructuring, and interpersonal communication, such as that developed by Allen et al.,32 for treatment of patients with medically unexplained symptoms, may be more effective in NFPD patients.
The results of this long-term follow-up study suggest that NFPD should be regarded as a subgroup of PD and that the course of NFPD is as severe as that of PD. Both groups have a significant impairment in health-related quality of life. However, the PD and NFPD patients have a somewhat different pattern of symptomatology. It seems that the PD patients develop more of the comorbid disorders that are well known to complicate PD; these include alcohol abuse29 and major depression;30 and that NFPD patients suffer from more comorbid somatoform disorders, as well as periods of depression. Although many of the NFPD patients develop panic attacks with fear, their reported psychological distress is low. This may have clinical implications because these patients will probably not be referred for psychiatric treatment, but rather seen in somatic practice, which they consult because of a range of somatic diseases, as well as pain. The results of this study emphasize the need for physicians in cardiological settings or in primary care to bear in mind that it is possible to fulfill the diagnostic criteria for PD without experiencing free-floating anxiety or fear, because patients with NFPD have reduced health-related quality of life and increased healthcare utilization and are, therefore, are in need of treatment.
Study Strengths and Limitations
The strengths of this study are that we followed the patients for a long period of time and performed psychiatric and cardiological reevaluation after 9 years. However, we did not collect data regularly throughout the follow-up period. Therefore, we do not know whether the findings at the time of follow-up reflect the psychiatric and medical morbidity of the patients throughout the 9-year period. Another important issue is whether the differences in psychiatric diagnosis from baseline to follow-up are reliable and not caused by different judgment by the interviewers. However, the last author of this article, who performed the baseline interviews, was the one who made a second evaluation of the interviews at follow-up, and the interrater reliability scores were high. Furthermore, no systematic evaluation of medical disorders other than CAD was conducted; however, that was not considered to be the main aim of this study.
Dealing with a small study group such as the NFPD patients, which consisted of 17 people at baseline and only 11 at follow-up, weakens the statistical power of the study and makes it susceptible to Type II errors. Differences between the NFPD and PD patients may thus actually be significant, although they are statistically not significant in the current sample. This may be the case when comparing the two groups regarding current major depression and prevalence of any psychiatric disorder. However, most of our results showed that differences between the NFPD and PD patients were either clearly not significant or clearly significant.
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CONCLUSION
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This long-term follow-up study of NFPD patients supports the position that NFPD is a subgroup of PD, because the majority of NFPD patients experience panic attacks with fear during the course of their illness. The outcome of NFPD patients is as severe as that of the PD patients regarding health-related quality of life, although the symptom profiles of the two groups differ somewhat. Because the reported psychological distress of NFPD patients stays low, these patients will probably not be referred to psychiatric treatment, but, rather, are seen in general (somatic) practice, which they consult because of a range of somatic symptoms and diseases. It is therefore especially important for physicians in cardiological settings or primary care to bear in mind that it is possible to fulfill the diagnostic criteria for PD without experiencing free-floating anxiety or fear. These patients have reduced health-related quality of life and increased healthcare utilization and are, therefore, in need of treatment. The challenge is to make primary-care physicians aware of this subgroup of PD and, further, to educate and motivate the patients to receive psychiatric treatment even if they do not directly experience psychiatric symptoms.
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ABSTRACT
INTRODUCTION
