Panic disorder: evidence for genetic vulnerability

Linkage genome scan for loci predisposing to panic disorder or agoraphobia

We conducted a 10 cM linkage genome scan in a set of 20 American pedigrees (153 subjects), ascertained through probands with panic disorder (PD). Several anxiety disorders segregate in these families; they were diagnosed on the basis of Schedule for Affective Disorders and Schizophrenia interview. In this article, we describe results for panic disorder and agoraphobia, which are closely related, common, heritable anxiety disorders. This is the first complete linkage genome scan for agoraphobia and the third for PD. A total of 407 markers (389 autosomal, 18 X chromosome) were genotyped. Multipoint LOD score and NPL analysis were completed using GENEHUNTER2. For PD, two genomic regions meet criteria for suggestive linkage. One of these regions is on chromosome 1 (LOD score = 2.04). This region coincides with a region that generated a LOD score of 1.1 in a previous genome scan by Crowe et al. [2001: Am J Med Genet (Neuropsychiatr Genet) 105:105-109]. The other (LOD score = 2.01) is located on chromosome 11p and occurs at marker CCKBR, one of eight candidate genes examined. For agoraphobia, the most promising potential linkage was on chromosome 3 (NPL score = 2.75; P = 0.005). This was accounted for primarily by a single family that by itself generated an NPL score of 10.01 (P = 0.0039) and a LOD score of 2.10. These results provide initial evidence for a genetic locus on chromosome 3 that contributes to risk for agoraphobia. They also support suggestive linkage to two risk loci for panic disorder. Additional potential loci were identified with lesser statistical support; several of these were consistent with previously reported panic disorder linkage results. Overall, the results presented here suggest that PD and agoraphobia are complex traits that share some, but not all, of their susceptibility loci. Published 2001 Wiley-Liss, Inc.

A family study of anxiety disorders: familial transmission and relationship to mood disorder and psychoactive substance use disorder

The prevalence of mental disorders in 76 first-degree relatives (parents and nontwin siblings) of 33 subjects with anxiety disorder was compared with the prevalence of mental disorders in 45 first-degree relatives of 20 subjects with mood disorder and 13 first-degree relatives of 6 subjects with psychoactive substance use disorder. All subjects were personally interviewed with the Structured Clinical Interview for DSM-III-R Axis I (SCID I). Interrater reliability was high for most diagnoses. Significantly more first-degree relatives of subjects with anxiety disorder had panic disorder and generalized anxiety disorder compared with relatives of probands with mood disorder. Significantly more female than male relatives of anxiety subjects suffered from anxiety disorders; there were no gender differences in the prevalence of anxiety disorders in relatives of mood and psychoactive substance use disorder (PSUD) subjects. The combination of anxiety and mood disorder was overrepresented in first-degree relatives of subjects with the same type of comorbidity. In relatives of subjects with mixed anxiety and psychoactive substance use disorder, but no mood disorder, there was an overrepresentation of PSUD; mainly alcohol abuse or dependence.

Family genetic studies of panic disorder

A review of family and twin studies using specified diagnostic criteria shows the highly familial nature of panic disorder and suggests evidence for a genetic etiology. The population-based lifetime rates of panic disorder cross-nationally range between 1.2/100 and 2.4/100, whereas, the lifetime rates in first-degree relatives of panic probands range between 7.7/100 and 20.5/100. There is evidence from family and twin studies for the separation of panic disorder and generalized anxiety disorder. While there is a substantial comorbidity in individuals between panic disorder and major depression, these two disorders are separate conditions which are independently and specifically transmitted within families. The mode of transmission of panic disorder remains unclear. The high lifetime rates of panic disorder, strong evidence for vertical transmission, and the potential biological markers have increased interest in the application of modern linkage techniques. Several genetic linkage studies of panic disorder are ongoing.

Further evidence of an association between behavioral inhibition and anxiety disorders: results from a family study of children from a non-clinical sample

Behavioral inhibition to the unfamiliar, identifiable in early childhood and reflecting the tendency to exhibit withdrawal and excessive autonomic arousal to challenge or novelty, has been found to be prevalent in young offspring of parents with panic disorder and agoraphobia and associated with risk for anxiety disorders in these children. Using family study methodology, we now examine psychopathology in first degree relatives of children from a non-clinical longitudinal cohort identified at 21 months of age as inhibited (N = 22) or uninhibited (N = 19) and followed through the age of seven years for a study of preservation of temperamental characteristics in normal children. These assessments were compared with evaluations of the first degree relatives of 20 normal comparison children. Psychiatric assessments of parents (N = 110) and siblings (N = 72) were based on structured interviews conducted blindly to the temperamental classification of the index child. Parents of inhibited children, compared with parents of uninhibited and normal controls, had significantly higher risks for multiple (greater than or equal to 2) anxiety disorders, continuing anxiety disorders (both a childhood and adulthood anxiety disorder in the same parent), social phobia, and childhood avoidant and overanxious disorders. These findings provide additional support for the hypothesis linking behavioral inhibition with risk for anxiety disorder.

A family panics

We report the treatment of a family in which both spouses developed panic disorder, and their son, school phobia, soon after the death of a close relative. The interactional style observed within this family suggested that interpersonal factors were important in the generation of anxiety in each member. Detailed case histories such as the one we report underscore the importance of a systemic perspective when assessing individuals who present with anxiety disorders.