Exercise tolerance in panic disorder patients

Sixteen panic patients and fifteen normal controls performed submaximal exercise testing on a bicycle ergometer. Only one patient subject panicked. Biochemical, physiological, and psychological data showed similar exercise tolerance in both patients and controls. Exercise-induced distress and lactate increment do not appear to cause panic attacks.

Panic-like attack induced by microinfusion into the locus coeruleus of antagonists and inverse agonists at GABAA-receptors in rodents

The microinfusion of drugs inhibiting GABA-ergic transmission into the locus coeruleus (LC) of rats and mice produced a dramatic pattern of behavioural stimulation accompanied by marked electrocortical (ECoG) desynchronization. In rats, unilateral microinfusion into the LC of bicuculline (0.5-4 pmol) produced dose-dependent behavioural stimulation culminating in a panic-like attack, ECoG desynchronization and marked changes in ECoG spectrum power. These effects were prevented by a pretreatment into the same site with muscimol. Similarly, in mice, the microinfusion of ethyl-beta-carboline-3-carboxylate (beta-CCE, 4.1 nmol) into the LC of C57BL/6 mice produced an intense state of behavioural stimulation accompanied by intense stereotyped movements and increased excitability to external stimuli; these effects were prevented by prior microinfusion of diazepam or flumazenil into the same site. In conclusion, the present experiments show that in rodents drug manipulations leading to a decrease in the activity of GABA-benzodiazepine receptor complex in the LC are responsible for the occurrence of panic-like attacks.

Neuroendocrine effects of diazepam in panic and generalized anxiety disorders

The adrenocorticotropic hormone (ACTH), cortisol, and growth hormone responses to four consecutive, logarithmically increasing doses of intravenous diazepam compared with placebo given at 15-min intervals were examined in patients with panic disorder (n = 13), generalized anxiety disorder (n = 8), and healthy controls (n = 13). Diazepam caused dose-dependent decreases in cortisol and increases in GH and dose-independent decreases in ACTH. There were no patient-control differences, possibly due to either the small sample size of the experimental paradigm, which tested subjects in an upright, sitting position in mildly arousing circumstances.

Noncardiac chest pain in patients with heart disease

This is a retrospective study of cardiac patients with noncardiac chest pain referred for evaluation of esophageal motility. Sixty-eight patients with heart disease were compared with 210 patients without heart disease according to findings from symptom questionnaires and a psychologic test (Brief Symptom Inventory). More than 70% of each group qualified for an anxiety or depressive diagnosis on the symptom questionnaire. These diagnoses were supported by significant elevations of scores on the anxiety and depression scales of the Brief Symptom Inventory. Male gender and a diagnosis of panic disorder occurred significantly more often in the patients with heart disease. "Stress" was cited as the cause of illness in about half the sample, but this led to less than satisfactory rates of psychiatric evaluation or pharmacotherapy. This is of particular concern for the cardiac patients because of the known adverse effect of anxiety and depression in those with heart disease.

The QKd interval in panic disorder: an assessment of end-organ thyroid hormone responsivity

The QKd interval was utilized as a presumptive index of end-organ thyroid hormone effect to test the hypothesis that patients with panic disorder might have abnormal tissue-level responsivity to normal levels of peripherally circulating thyroid hormones. No significant differences in QKd intervals were found between 15 patients with panic disorder (230 +/- 50 msec) and 20 normal controls (224 +/- 29 msec) while drug-free. These findings suggest that patients with panic disorder have normal tissue-level responsivity to thyroid hormone.

Serotonin receptor sensitivity and aggression

This study investigated the relationship between increased serotonin (5-hydroxytryptamine, 5HT) receptor sensitivity and human aggression. A low oral dose of meta-chlorophenylpiperazine (MCPP), a postsynaptic 5HT receptor agonist, was administered in a placebo-controlled design to depressed (n = 22) and panic disorder (n = 20) patients classified with or without signs of outwardly directed aggression, patients with a history of suicide attempts (inwardly directed aggression) (n = 11), and normal controls (n = 19). Hormones under 5HT control were measured at 30-min intervals. Results were as follows: (1) MCPP did not induce or reduce anger, (2) patients with outwardly directed aggression did not have significantly greater MCPP-induced cortisol or prolactin release than did patients without signs of outwardly directed aggression, (3) patients with a history of suicide attempts did not have significantly greater MCPP-induced cortisol or prolactin release than did normal controls, and (4) MCPP-induced hormone release was unrelated to measures of aggression.

Heart rate variability in patients with major depression

We have previously reported decreased heart rate variability upon standing in panic disorder patients compared with controls. In this study, we extend our report to include patients with major depression (n = 19). Compared to normal controls (n = 20) and panic disorder patients (n = 30), there was no significant difference in the immediate changes in heart rate upon standing in the depressed group. The standing heart rate variability (R-R variability) was significantly lower in panic disorder patients compared to both normal controls and depressed patients as indicated by the corrected standard deviations, the corrected mean consecutive difference, the corrected standard deviation of the mean consecutive difference of the R-R intervals, and the high frequency variability in successive R-R intervals, suggesting an increased vagal withdrawal in panic disorder patients, especially upon standing. There was no significant difference in any of the heart rate variability measures between depressed patients and normal controls.

Pituitary hormone responses to meta-chlorophenylpiperazine in panic disorder and healthy control subjects

The present study reports adrenocorticotropic hormone (ACTH) and prolactin responses after oral administration of 0.25 mg/kg of the serotonin agonist, meta-chlorophenylpiperazine (MCPP), in patients with panic disorder (PD) and in healthy subjects. MCPP blood levels were similar for the two groups, but almost twice as high in males as in females. Female patients had augmented ACTH and prolactin release as compared to healthy females, while ACTH and prolactin release in male patients was similar to that of male controls. These results suggest that female PD patients have hypersensitive serotonin receptors. Moreover, they indicate that pharmacokinetic gender differences may affect challenge studies, and that different doses may be required to study neuroendocrine responses in males and females.

The effects of physostigmine infusion on patients with panic disorder

Nine patients who met both DSM-III and RDC criteria for panic disorder and nine age-matched normal controls received infusions of physostigmine. The patients and normal controls did not differ in either their self-reported or the observer-reported ratings of anxiety, mood, or activation. The two subject groups also did not differ in blood pressure, pulse, or cortisol responses to physostigmine. Physostigmine did not provoke panic attacks in either the control or patients groups.

New ways of treating panic disorder

The research evidence strongly suggests that the most effective form of treatment for panic disorder is cognitive therapy. It is more practical, however, to initiate treatment with alprazolam or with imipramine. Either drug will suppress symptoms and even a half of the patients will stay well.

Cerebrospinal fluid levels of monoamine metabolites in panic disorder

The cerebrospinal fluid (CSF) levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5HIAA), the noradrenaline metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG), and the dopamine metabolite homovanillic acid (HVA) did not differ significantly in a group of patients with panic disorder (n = 17) as compared to age- and sex-matched normal controls (n = 17). While CSF concentrations of HVA and 5HIAA were significantly correlated in both patients and controls, CSF MHPG levels were significantly correlated with the concentrations of CSF 5HIAA and HVA only in patients. In a small number of subjects (n = 5), successful reduction of anxiety attacks by administration of clomipramine or imipramine (50-150 mg/day) for at least 2 months was associated with a significant decrease in CSF concentrations of 5HIAA and MHPG, but not HVA.

Pituitary microadenoma presenting as panic attacks

A woman with pituitary microadenoma presented with panic attacks. This case illustrates the need both for routine medical screening of psychiatric patients and for psychiatrists to remain aware of the clinical features of medical syndromes.

Chest muscle activity and panic anxiety: a preliminary investigation

This report represents a pilot investigation of the role of chest muscle electromyographic (EMG) activity in developing panic episodes. Chest EMG activity was obtained as part of a larger study examining ventilatory differences between panic sufferers and normal controls. Frontalis EMG, heart rate, and minute ventilation (breathing rate and tidal volume) were also obtained during the study. The ventilatory procedure involved exposing the subjects to three periods of carbon dioxide gas inhalations (1%, 3%, 5%; balance oxygen). Subjective measures of frightening cognitions and body sensations were obtained across the inhalation phases as well. The panic disorder subjects were divided, on the basis of subjective anxiety ratings obtained throughout the study, into high anxious (HA) and low anxious (LA) panic disorder groups. The HA panic disorder patients exhibited significantly higher chest EMG activity than the LA panic disorder patients and controls across all phases of the experiment. In addition, the chest EMG predicted, better than the other physiologic measures, the number of frightening cognitions and sensations reported by the subjects during the baseline and 5% CO2 inhalation phases. Overall, the results were supportive of the further study of chest wall EMG activity in the pathogenesis of panic attacks.

Psychophysiological response patterns in panic disorder

To determine whether panic disorder patients exhibit physiological hyperarousal during rest or during mild, non-panic-inducing stress, 18 patients who experienced frequent panic attacks were compared with nonanxious controls on a battery of physiological assessments. During baseline, patients with panic disorder exhibited higher forehead electromyographic activity, higher systolic blood pressure and higher heart rates than non-anxious volunteers. During psychological stress, heart rate and systolic blood pressure rose more in patients with panic disorder than in nonanxious controls. The skin conductance response, however, was greater and more variable in the nonanxious controls. The results suggest that panic disorder patients with frequent panic attacks exhibit heightened cardiovascular arousal and decreased electrodermal flexibility than nonanxious people, even in nonthreatening situations.

The test-retest reliability of the hyperventilation provocation test

The hyperventilation provocation test (HPT) has been widely used for reproducing symptoms of panics. It is assumed that subjects experience similar symptoms on consecutive occasions of hyperventilation. Fourteen subjects with a history of panics and fourteen without such a history underwent the HPT on two occasions one week apart. In the group of 28 subjects as a whole, there were moderate similarities between the HPTs in both the choice and severity of symptoms reported, even when pre-existing symptoms were controlled statistically. Nevertheless, in the subject-by-subject analysis, many subjects showed no resemblance between the two HPTs in the choice of symptoms. This suggests that many subjects would not show any resemblance between the symptoms experienced in an HPT and those of their latest panic even if hyperventilation occurred in that panic.

The application of genetic methods to the study of disease associations in psychiatry

The problem of multiple diagnoses in the same patient is a very real one in psychiatry. Theoretical causes of disease associations are reviewed and illustrated with examples from a variety of psychiatric conditions. These include Huntington's disease and depression, mitroprolapse and panic attacks, anxiety disorder and depression, and others.

Comparison of panic disordered patients with high versus low MHPG

Fourteen panic disorder patients with low 3-methoxy-4-hydroxyphenylglycol (MHPG) were compared to 14 patients with high MHPG. Patients with low MHPG were more likely during the preceding month to have experienced spontaneous panic attacks (P less than 0.008) than were patients with high MHPG. Patients with high MHPG had increased severity ratings on several individual symptoms of anxiety.

Abnormal zymosan-induced neutrophil chemiluminescence as a marker of depression

Preliminary studies have shown that polymorphonuclear neutrophil (PMN) activity is decreased in a state-dependent manner in patients with endogenous depression. The present study investigates this finding in a larger group of psychiatric patients and attempts to determine the identification of the factor responsible for the abnormal neutrophil function. Chemiluminescence responses of PMNs from patients with diagnoses of endogenous depression, panic disorder, anxiety, schizophrenia and alcoholism were assessed concurrently with age- and sex-matched control subjects. The reduction in PMN activity was observed in panic disorder patients as well as during depression but remained normal in schizophrenia, alcoholism and generalised anxiety. The defect in PMN function appears to be related to an abnormal factor in the serum of the patient which is corrected on clinical recovery. Aspirin-inhibited prostaglandin synthesis resulted in an enhancement of PMN activity in healthy subjects, suggesting a possible role for prostaglandins in the abnormal PMN response.

Cardiovascular dystonia in recovered panic patients

Resting heart rate, heart rate variability and blood pressure; the heart rate and blood pressure response to standing; and the heart rate response to Valsalva's manoeuvre, have been measured in a group of 12 patients with panic disorder and a group of 12 age- and sex-matched normal subjects. The patients had undergone treatment for their panic attacks with cognitive therapy; all had responded and all had been panic-free for a minimum of 4 months (mean 7.6 months). Mood ratings (BDI, BAI and SSAI) were comparable with established norms. The patients nevertheless had a raised resting systolic blood pressure, a reduced resting heart rate and an abnormal orthostatic response.

Anxiety and the menstrual cycle in panic disorder

Nineteen females with panic disorder were studied using daily prospective home diary ratings of various general health related items, a short anxiety self-rating scale, a survey of late luteal phase dysphoric symptoms, as well as a record of the number and severity of panic attacks. The subjects collected information for 60 consecutive days, and information regarding 30 menstrual cycles was available for analysis. Overall, subjects retrospectively reported increases in their anxiety symptoms during premenstrual days, but this was not demonstrated consistently on daily prospective ratings.

Adrenergic status in anxiety disorders: platelet alpha 2-adrenergic receptor binding, blood pressure, pulse, and plasma catecholamines in panic and generalized anxiety disorder patients and in normal subjects

In order to evaluate adrenergic function in anxiety disorders, platelet alpha 2-adrenergic binding parameters and supine and standing blood pressure, pulse, and venous plasma epinephrine and norepinephrine were determined in patients with panic attacks or generalized anxiety disorder and in normal subjects. The maximum number of binding sites (Bmax) for the partial agonist tritiated clonidine was significantly lower for both patient groups than for normal subjects, and the Bmax for the antagonist tritiated yohimbine was significantly lower for panic patients. There were no other substantive differences across groups. Prior exposure to psychotropic drugs might account for the results for clonidine binding, but not for yohimbine. The Bmax for clonidine was correlated with norepinephrine increases upon standing and, for panic patients, with the severity of full unexpected panic attacks. These data provide further evidence of adrenergic receptor abnormalities in people with anxiety disorders.

A cerebrospinal fluid study of the pathophysiology of panic disorder associated with alcoholism

In order to investigate the neurochemistry of panic disorder in alcoholics, we measured various cerebrospinal fluid (CSF) parameters in subjects with both conditions and compared them with an age- and sex-matched population of alcoholics and normal controls. When height, age and weight were covaried, subjects with panic disorder had higher levels of B-endorphin in CSF. There were no differences in other CSF measures between the groups. Alcoholics with panic disorder had higher plasma MHPG concentrations compared with alcoholics without panic disorder but these were not statistically different from controls.

Comparison of panic symptom sequences and pathophysiologic models

In an attempt to assess which of the proposed etiologic models best accounts for the symptomatology seen in panic attacks, 21 patients with panic attacks were asked to describe the symptom sequence during an attack. Using the Kolmogorov-Smirnov test, the Runs test, and Friedman's 2-way ANOVA, the degree of agreement between their attacks, and the proposed models was assessed. All three analyses suggest that, at the 0.1, 0.025, and 0.05 levels of significance respectively, the autonomic dysfunction model best accounts for the sequence of symptoms in panic attacks.

Decreased R-R variance in panic disorder patients

To investigate autonomic function in panic disorder patients (n = 30), we compared postural changes in heart rate and the R-R interval variance in patients and normal controls (n = 20). There was no significant difference in the immediate changes in heart rate upon standing between the groups. R-R variance was significantly decreased during resting supine condition in patients as indicated by the corrected standard deviation of the R-R intervals. The standing R-R variance was significantly lower than that of normal controls as indicated by the corrected standard deviations, the corrected mean consecutive difference and the corrected standard deviation of the mean consecutive difference of the R-R intervals, suggesting an increase in vagal withdrawal in patients, especially upon standing. If this finding is specific to panic disorder patients, it may be a useful peripheral marker for this condition.

High-affinity platelet [3H]LSD binding is decreased in panic disorder

Platelet [3H]LSD binding was measured in 15 patients with panic attacks and 15 controls. The mean (+/- SD) Bmax values of the patients (14.1 +/- 6.3 fmol/mg protein) and of the controls (18.5 +/- 4.7 fmol/mg protein) were significantly different (P less than 0.05, Mann-Whitney U-test). Mean (+/- SD) values of Kd for the patients (0.55 +/- 0.34 nM) and for the controls (0.51 +/- 0.12 nM) were not significantly different (P greater than 0.1, Mann-Whitney U-test). The results are discussed in terms of a serotonergic hypothesis of the aetiology of panic disorders.

Hyperventilation and panic attacks

The role of hyperventilation in the aetiology of panic attacks is still unclear. This paper briefly reviews the role of hyperventilation and abnormal respiration to panic attacks and examines the experimental evidence. Evidence has been found that physiological variables such as paCO2 and pH are involved in the aetiology of panic attacks and panic disorder but the extent and the nature of the involvement of cognitive variables is undetermined. Based on current evidence, there is a need to integrate cognitive variables with the physiological framework proposed by the hyperventilation theory. Until clear experimental evidence is produced about the relationships between cognitive and physiological factors, the applicability of hyperventilation in the aetiology and treatment of panic attacks remains in question.

Paradoxical growth-hormone responses to thyrotropin-releasing hormone in panic disorder

Thyrotropin-releasing hormone (TRH) has been reported to stimulate growth hormone (GH) release in a variety of pathological conditions, including some studies of major depression. Because of the considerable phenomenological and neuroendocrine overlap between major depression and panic disorder, we investigated the rate of positive GH responses to TRH in 38 patients with panic disorder and 23 normal controls. There were no between-group differences in mean GH response to TRH or in the proportion of subjects with positive responses. These findings are discussed in the context of neuroendocrine regulation of GH secretion and the relationship between anxiety and affective disorders.

Major depression and agoraphobia in patients with angiographically normal coronary arteries and panic disorder

Patients with panic disorder and/or agoraphobia appearing in psychiatric settings report rates for lifetime major depression between 24% and 91%. Between 40% and 90% of patients with panic disorder in psychiatric populations report concomitant agoraphobia. A recent study of panic disorder subjects appearing in an outpatient cardiology clinic confirmed the strong link between panic and depression but found only a weak association between panic disorder and agoraphobia. In order to test the reliability of these outpatient cardiology findings, the authors studied major depression and agoraphobia in patients with angiographically normal coronary arteries and panic disorder. Twelve of the 32 (37.5%) panic disorder subjects reported a lifetime history of major depression (nine current, three past only). Only two of the 32 (six percent) reported any phobic avoidance. This study confirms the previous findings which suggest that major depression is common in cardiology populations with panic disorder and that phobic avoidance is uncommon in this group.

Cardiac left ventricular hypertrophy and chamber dilatation in panic disorder patients: implications for idiopathic dilated cardiomyopathy

Echocardiographic comparison of 35 panic disorder patients to 35 normal control subjects found subclinical increases of cardiac left ventricular chamber size in eight panic patients (and one control subject), and of left ventricular mass (corrected for body surface area) in seven panic patients. There was a significantly greater variance of left heart chamber size and corrected mass in panic patients compared with control subjects, without significant group mean differences. Consistent with a previously reported association of panic anxiety and idiopathic dilated cardiomyopathy, this study suggests that some healthy panic patients may have subclinical myocardial changes.

Five percent carbon dioxide challenge: valid analogue and marker of panic disorder?

The administration of 5% carbon dioxide (CO2) to patients with panic disorder (PD) induces a behavioral response similar to a naturally occurring panic attack. This article reviews the literature on the nature and incidence of this response. We conclude that the 5% CO2 challenge test is a valid and useful laboratory analogue of naturally occurring panic attacks, and shows promise as a marker to identify a subset of PD patients. Though further research on reliability, validity, and dose-response effects must be conducted, the CO2 challenge test provides important information regarding the phenomenology of panic states.

Peripheral catecholamine levels and the symptoms of anxiety: studies in patients with and without pheochromocytoma

We studied the correlation of plasma and urinary epinephrine (E) and norepinephrine (NE) levels with anxiety symptoms in three patient groups: 1) pheochromocytoma (PH+) (n = 17); 2) hypertensives with elevated catecholamine levels shown not to have a PH (PH-) (n = 25); and 3) patients with panic disorder (PD) (n = 23). Structured interviews and four self-rated anxiety scales were used: the SCL-90R Anxiety and Phobic Anxiety scales, and the Spielberger State/Trait Anxiety Inventories. The SCL-90R Somatization scale (which measures 12 somatic symptoms) was also utilized. None of the PH+ patients met DSM-III criteria for PD. Two met criteria for generalized anxiety disorder (GAD). Of the PH- patients, two had PD, two had GAD, and three had both. Urinary and plasma E did not show significant positive correlations with any of the four anxiety scales in any of the three patient groups. In both the PH+ and PH- groups, E was significantly correlated with the SCL-90R Somatization scale. NE was not significantly correlated with any of the four anxiety scales in the PH+ group. In contrast, in the PH- group, plasma NE was significantly correlated with anxiety on all anxiety scales (r = +0.55 to +0.77, p less than 0.05). Furthermore, in the PH- group, plasma NE was significantly correlated with those items of the SCL-90R Anxiety scale measuring the cognitive rather than the noncognitive symptoms of anxiety. In the PD group as well, plasma NE showed a significant correlation with the SCL-90R Anxiety Scale (r = +0.67, p less than 0.05). Taken together, our observations suggest that: 1) the effects of catecholamines in the periphery derived from a source independent of nervous system control (such as a PH) are not sufficient to elicit an anxiety disorder meeting DSM-III criteria; and 2) in patients without an autonomous source of peripheral catecholamines, NE in the periphery results from sympathetic nervous system activation and probably reflects, rather than causes, anxiety.

[Review of recent empirical studies of the classification, pathogenesis and therapy of anxiety disorders]

Beginning with the eighties, a paradigm-change concerning anxiety disorders has taken place in considerable parts of psychiatry. Anxiety disorders are no longer regarded as consequences of conflicts and ineffective defences or as concomitants of other psychiatric disorders but rather as disorders of their own. This resulted in a modified outlook on anxiety disorders focusing on the acute panic attack (Panic disorder) instead of focusing on chronic anxiety (Anxiety neurosis). This paper reviews recent empirical studies concerning classification, pathogenesis, and therapy of anxiety disorders, i.e. after introduction of the concept of Panic disorder. Epidemiological studies could demonstrate that in western countries anxiety disorders account for the most frequent psychiatric disorders with prevalence rates of 2.0% to 4.7%. Panic disorders show prevalence rates of 0.4% to 1.1%. Results of recent follow-up studies indicate a favorable course for outpatients and an unfavorable course for inpatients with anxiety disorders. Family studies reported on positive familial loading for Panic disorder but not for Agoraphobia and Generalized anxiety disorder. A twin study found higher concordance rates for panic attacks and Agoraphobias in monozygotic twins than in dizygotic twins. Pharmacological provocation studies with lactate infusion, CO2-inhalation, and administration of Caffeine, Yohimbine, Isoproterenol showed a higher vulnerability of patients with Panic Disorder as compared to healthy controls. However, all studies display methodological short-comings and could be interpreted differently as to the concept of a biologically determined vulnerability. Provocation studies using inverse Benzodiazepine-agonists dealt only with healthy probands. Whereas life events play a rather unimportant role für the pathogenesis of anxiety disorders, recent studies point to the influence of cognitive processes and personality variables for the pathogenesis of anxiety disorders. Concerning treatment of anxiety disorders and especially of panic disorders, pharmacological studies as well as studies of behavioural therapy indicate very good results for acute treatment and good results for behavioural therapy with respect to one to four year follow-up studies. Recently, combined drug and psychotherapy gains growing interest. Conclusions are drawn with respect to the usefulness of the new classification, i.e. after the introduction of Panic disorder as a diagnostic category, and references are given for further research strategies.

No evidence of interference of hypocapnia/respiratory alkalosis with classical conditioning of electrodermal responses

Most phobias can be traced to aversive experiences relating to the phobic cue, but most aversive experiences do not result in phobias. Why is it that only sometimes these experiences result in classical conditioning of fear? It was hypothesized that if the subject is in a state of hypocapnia/respiratory alkalosis, classical conditioning of fear is facilitated, while extinction of fear responses is inhibited. Thirty-two healthy volunteers underwent a classical conditioning procedure with slides as conditioned stimulus, electric shocks as unconditioned stimulus, and electrodermal responding as (un) conditioned response. During conditioning, half of the subjects hyperventilated and were hypocapnic/alkalotic, while the other half was not. In both groups clear conditioning occurred, but there was no effect of hypocapnia. Results are critically discussed.

Comorbidity of panic disorder and major depressive disorder: effects on platelet alpha 2 adrenergic receptors

Adrenergic receptor dysregulation has been described as occurring in both major depressive disorder (MDD) and panic disorder. Measurements of platelet alpha 2 adrenergic receptors in these patients may be confounded by the coexistence or comorbidity of both diagnoses in the same patient. To explore this possibility, we measured platelet alpha 2 adrenergic receptors (3H-clonidine and 3H-yohimbine binding) in 3 groups of patients (MDD only, panic disorder only, and those showing comorbidity of MDD and panic) and normal controls. Patients with comorbidity of MDD and panic disorder had significantly lower agonist binding (3H-clonidine).

Alcoholism and panic disorder: is the comorbidity more than coincidence?

Studies on alcoholic patients have found a higher than expected prevalence of panic disorder, and suggest a positive correlation between the level of alcohol consumption and severity of anxiety. Conversely, there is an increased prevalence of alcoholism among patients with panic disorder and their blood relatives. A comparison of symptoms, physiological and neurochemical changes known to occur in both alcohol withdrawal and panic disorder reveals a degree of similarity between the 2 conditions. Based on the data, we propose that the chemical and cognitive changes occurring as the result of repeated alcohol withdrawals may kindle and condition coincidence of panic attacks in susceptible individuals. Implications of our postulates for treatment of alcohol withdrawal and panic disorder in alcoholics and for future studies are discussed.

Temporal lobe abnormalities in panic disorder: an MRI study

Brain mapping studies have shown abnormal changes in cerebral blood volume and oxygen consumption, or other neurophysiological abnormalities, in panic disorder (PD) patients. Because of these intriguing reports, we decided to assess the neuroanatomical aspects of patients with PD using magnetic resonance imaging (MRI). We included 31 consecutive cases with a diagnosis of PD according to the DSM-III criteria, and 20 controls. All subjects had to be right-handed and between 20 and 40 years of age. The usual exclusion criteria were applied. We carried out the MRI tests with a General Electric Signa Machine operating at 1.5 Tesla. Over 100 images were obtained per patient with an emphasis on assessing temporal lobe. There were no significant differences in age, gender, or weight between the patients and controls. We found a statistically significant higher number of abnormalities in PD patients (40%), as compared with the controls (10%). The most striking findings were focal abnormalities in the temporal lobes: areas of abnormal signal activity, and asymmetric atrophy of the temporal lobe occurred mostly on the right side. These results implicated the limbic system and may prove to be of particular relevance in panic and phobic disorders. However, the significance of our findings remains unknown and challenging. Further MRI studies in PD will be required for a better understanding of the illness.

Hypercarbia versus hypocarbia in panic disorder

In order to compare the panicogenic effects of hypercarbia and hypocarbia in panic disorder (PD), 12 PD patients and 11 healthy controls underwent a 35% CO2 challenge as well as a hyperventilation provocation test in a random cross-over design. Both anxiety and anxiety symptoms proved to be significantly higher during the 35% CO2 challenge in PD patients as compared to the response during 35% CO2 in normals and during hyperventilation in both patients and normals. The results suggest that PD patients are specifically hypersensitive to an increase in pCO2.

[Neurotransmitters in anxiety and panic disorders]

The currently available empirical findings lead us to assume that various forms of anxiety disorders--such as generalised anxiety syndrome or panic disorder--are based on different pathophysiological mechanisms with varying involvement of different neurotransmitter systems. We must bear in mind that whereas the disturbance of a transmitter may predominate--such as the disturbance of the noradrenalin system in panic disorder and that of the GABA-ergen system in generalised anxiety--on the other hand the transmitter systems are mutually interlinked, so that an isolated disturbance of a system is very unlikely. However, to the present date it has not been possible to give a definite biochemical characterisation of a certain disease pattern, such as that of panic disorder. Likewise, no unequivocal conclusions can be drawn in respect of cerebral localisation. Nevertheless, results obtained in animal experiments suggest that in panic disorder certain brain areas like e.g. the locus ceruleus may be affected. Future hopes rest in developing more specific drugs that selectively change a transmitter system and on new techniques such as positron emission tomography enabling a better insight into the mode of functioning of the brain. New possibilities seem to be offered also by defining a predisposition via molecular-genetic methods.

Heart rate and blood pressure changes during postural change and isometric handgrip exercise in patients with panic disorder and normal controls

Changes in heart rate (HR) and blood pressure (BP) were measured serially during postural changes and isometric hand grip exercise test (IHT) in 30 patients with panic disorder and 30 normal controls. Though there were no significant differences in the delta increase of HR or systolic or diastolic BP during these tests, the resting supine and standing diastolic BP were significantly higher in panic disorder patients than in controls. The standing mean BP was also significantly higher in panic disorder patients. These findings are suggestive of an increase in adrenergic tone in panic disorder patients.

Serotonin function in panic disorder: a double blind placebo controlled study with fluvoxamine and ritanserin

In order to evaluate serotonin (5-HT) function in panic disorder, a double blind placebo controlled study was conducted with ritanserin, a specific 5-HT2 receptor antagonist, and fluvoxamine, a selective 5-HT reuptake inhibitor, in 60 patients with panic disorder. Patients were treated for 8 weeks with 150 mg fluvoxamine, 20 mg ritanserin or placebo; these dose levels were reached after 1 week. In addition, as an index of 5-HT function in panic disorder, plasma concentration of beta-endorphin, cortisol and 5-hydroxyindolacetic-acid (5-HIAA) were measured. Furthermore, 5-HT uptake in blood platelets was assessed. Noradrenergic function was assessed by measuring plasma MHPG concentration. In addition, plasma melatonin concentration was measured. Treatment with fluvoxamine resulted in a profound reduction in the number of panic attacks, followed by a decrease in avoidance behavior. Treatment with ritanserin appeared to be ineffective. During treatment no significant changes were observed in plasma concentrations of beta-endorphin, cortisol, 5-HIAA and MHPG. With respect to 5-HT kinetics in blood platelets, a substantial increase in Km was observed after treatment with fluvoxamine, whereas Vmax decreased. After treatment with fluvoxamine, plasma concentration of melatonin was significantly increased, which suggests that melatonin synthesis is in part under serotonergic control. The findings of the present study do not support the hypothesis that 5-HT2 receptors are supersensitive in patients suffering from panic disorder, but allow no conclusions about the involvement of other 5-HT receptor subtypes.

Nocturnal panic: Response to hyperventilation and carbon dioxide challenges

To examine the role of ventilatory response in nocturnal panic, subjects experiencing nocturnal panic were compared with those who experienced daytime panic attacks only. In particular, measures of chronic hyperventilation (baseline pCO2) and CO2 hypersensitivity (response to ventilatory challenges) were assessed. Subjective and psychophysiological measures were obtained during baseline, forced hyperventilation, and carbon dioxide inhalation phases of a standardized laboratory-based assessment. The groups did not differ with respect to subjective or physiological measures or to the frequency with which panic occurred during the assessment. The results do not lend support to models that emphasize central CO2 hypersensitivity and chronic hyperventilation as primary mechanisms underlying nocturnal panic.