Genetic epidemiology of anxiety disorders

African-American representation in family and twin studies of mood and anxiety disorders: A systematic review

PURPOSE

Mood and anxiety disorders are common and disabling psychiatric disorders with known heritable risk factors. But the extent to which their heritability and familial risks can be generalized across ethnic/racial groups is still largely unknown, but remains of considerable scientific and clinical interest. The main objective in this review was to evaluate African-American (AA) representation in family and twin studies of major mood and anxiety disorders.

METHOD

We conducted key word-driven computerized searches in MEDLINE and PsycINFO and manual searches from reference lists of selected articles. Search parameters included family or twin studies, mood or anxiety disorders, and familial aggregation or heritability. US-based studies published from 1980 to 2015 were included.

RESULTS

The final selection yielded 209 studies, of which 88 did not report race/ethnicity or only reported Caucasian/white race. Of the remaining 121 studies, 66% did not include AAs, 24% included 1-10% AA, 8% included greater than 10% AA and 2 studies were exclusively AA. These trends were similar across study type, disorder and time periods spanning 35 years.

LIMITATIONS

Small samples, including the large number of studies without race/ethnicity reports, limited detailed analyses of change across time by disorder and study type. Adoption studies were not included in this review.

CONCLUSIONS

Underrepresentation of AAs in family and twin studies of affective disorders is substantial and can limit generalizability of established heritability and familial risk estimates across clinical and research settings. Additional twin and family studies focusing on AAs can be of benefit in closing this gap.

Determinants of the development of post-traumatic stress disorder, in the general population

PURPOSE

To assess (1) the lifetime prevalence of exposure both to trauma and post-traumatic stress disorder (PTSD); (2) the risk of PTSD by type of trauma; and (3) the determinants of the development of PTSD in the community.

METHODS

The Diagnostic Interview for Genetic Studies was administered to a random sample of an urban area (N = 3,691).

RESULTS

(1) The lifetime prevalence estimates of exposure to trauma and PTSD were 21.0 and 5.0%; respectively, with a twice as high prevalence of PTSD in women compared to men despite a similar likelihood of exposure in the two sexes; (2) Sexual abuse was the trauma involving the highest risk of PTSD; (3) The risk of PTSD was most strongly associated with sexual abuse followed by preexisting bipolar disorder, alcohol dependence, antisocial personality, childhood separation anxiety disorder, being victim of crime, witnessing violence, Neuroticism and Problem-focused coping strategies. After adjustment for these characteristics, female sex was no longer found to be significantly associated with the risk of PTSD.

CONCLUSIONS

The risk for the development of PTSD after exposure to traumatic events is associated with several factors including the type of exposure, preexisting psychopathology, personality features and coping strategies which independently contribute to the vulnerability to PTSD.

Nociceptin/orphanin FQ receptor antagonists as innovative antidepressant drugs

Nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) were identified in the mid 90s as a novel peptidergic system structurally related to opioids. A growing body of preclinical evidence suggests that blockade of NOP receptors evokes antidepressant-like actions. These have been explored using a range of compounds (peptide and non peptide antagonists), across different species (rat and mouse) and assays (behavioral despair and chronic mild stress) suggesting a robust and consistent antidepressant-like effect. Moreover, rats and mice knockout for the NOP receptor gene display an antidepressant-like phenotype in behavioral despair assays. Electrophysiological, immunohistochemical and neurochemical studies point to an important role played by monoaminergic systems, particularly 5-HTergic, in mediating the antidepressant-like properties of NOP antagonists. However other putative mechanisms of action, including modulation of the CRF system, circadian rhythm and a possible neuroendocrine-immune control might be involved. A close relationship between the N/OFQ-NOP receptor system and stress responses is well described in the literature. Stressful situations also alter endocrine, behavioral and neurochemical parameters in rats and chronic administration of a NOP antagonist restored these alterations. Interestingly, clinical findings showed that plasma N/OFQ levels were significantly altered in major and post-partum depression, and bipolar disease patients. Collectively, data in the literature support the notion that blockade of NOP receptor signaling could be a novel and interesting strategy for the development of innovative antidepressants.

Comprehensive review of generalized anxiety disorder in primary care in Europe

OBJECTIVE

This review aims to summarize meta-analyses and other relevant data relating to the efficacy and safety of the various treatment options for generalized anxiety disorder (GAD) in Europe. In addition, it will provide an overview of the prevalence, burden, and recognition of the disorder, with a view to raise awareness of GAD and inform primary care practitioners.

RESEARCH DESIGN AND METHODS

Relevant research or review articles on psychological or pharmacological treatments for GAD published in the English language between March 2006 and March 2012 were identified via a literature search in PubMed and ISI Web of Knowledge and from the Cochrane Library. Other relevant references/clinical guidelines were individually selected by the authors.

RESULTS

Prevalence rates of GAD vary across Europe but its economic and social burden is increasing. A large proportion of patients with GAD present with symptoms in primary care. However, due to the disorder's complexity and the incidence of comorbid diseases, some primary care physicians may lack the knowledge or confidence to effectively recognize, manage, and/or treat the disorder. This is despite psychological and pharmacological treatments being available for the effective management of GAD.

CONCLUSIONS

GAD remains a difficult disorder to detect and comorbid complications add to its economic and social burden. Early detection and intervention reduces the societal burden and improves GAD patients' quality of life and functional ability. Primary care practitioners play a key role in identifying and treating patients with GAD.

Childhood respiratory symptoms and mental health problems: the role of intergenerational smoking

OBJECTIVE

The aim of this study was to investigate the potential role of youth smoking, parental cigarette smoking and parental anxiety/depressive disorders in the relationship between respiratory symptoms and mental health problems among youth.

WORKING HYPOTHESIS

Adjusting for both parental smoking and parental anxiety/depressive disorders in the association between respiratory symptoms and mental health problems among young persons will significantly reduce the strength of the observed relationship.

STUDY DESIGN

Prospective cohort study. PATIENT-SUBJECT SELECTION: Data were drawn from a school-based sample of 1709 young persons in Oregon.

METHODOLOGY

Physical and mental health data were collected on youth.

RESULTS

Respiratory symptoms were associated with significantly increased odds of mental health problems among youth. After adjusting for youth smoking, the relationship between respiratory symptoms and depressive disorders was no longer statistically significant. The relationships between respiratory symptoms and anxiety and depressive disorders were no longer significant after adjusting for parental smoking. Parental anxiety/depressive disorders did not appear to influence these relationships.

CONCLUSIONS

These results provide initial evidence that exposure to parental smoking may play a role in the observed co-occurrence of respiratory and mental health problems in youth, and youths' own smoking appears to influence the link with depressive disorders, but not anxiety disorders.

Developmental epidemiology of anxiety disorders

This review focuses on developmental aspects in the epidemiology of anxiety disorders including prevalence, onset, natural course, longitudinal outcome, and correlates and risk factors, with focus on childhood through young adulthood. Anxiety disorders are frequent and early-emerging conditions. They may remit spontaneously; however, the same or other mental disorders often recur. Although risk factors have been identified, more work is needed to identify the most powerful predictors for onset and the progression to more complex forms of psychopathology and to understand the underlying mechanisms and interactions. This identification is crucial to facilitate research prevention, early interventions, and treatment programs.

The structure of genetic and environmental risk factors for phobias in women

BACKGROUND

To explore the genetic and environmental factors underlying the co-occurrence of lifetime diagnoses of DSM-IV phobia.

METHOD

Female twins (n=1430) from the population-based Norwegian Institute of Public Health Twin Panel were assessed at personal interview for DSM-IV lifetime specific phobia, social phobia and agoraphobia. Comorbidity between the phobias were assessed by odds ratios (ORs) and polychoric correlations and multivariate twin models were fitted in Mx.

RESULTS

Phenotypic correlations of lifetime phobia diagnoses ranged from 0.55 (agoraphobia and social phobia, OR 10.95) to 0.06 (animal phobia and social phobia, OR 1.21). In the best fitting twin model, which did not include shared environmental factors, heritability estimates for the phobias ranged from 0.43 to 0.63. Comorbidity between the phobias was accounted for by two common liability factors. The first loaded principally on animal phobia and did not influence the complex phobias (agoraphobia and social phobia). The second liability factor strongly influenced the complex phobias, but also loaded weak to moderate on all the other phobias. Blood phobia was mainly influenced by a specific genetic factor, which accounted for 51% of the total and 81% of the genetic variance.

CONCLUSIONS

Phobias are highly co-morbid and heritable. Our results suggest that the co-morbidity between phobias is best explained by two distinct liability factors rather than a single factor, as has been assumed in most previous multivariate twin analyses. One of these factors was specific to the simple phobias, while the other was more general. Blood phobia was mainly influenced by disorder specific genetic factors.

Familial influence of substance use disorder on emotional disorder across three generations

The concomitant influence of grandparental (Generation 1; G1) and parental (G2) substance use disorder (SUD) on grandchild (G3) emotional disorder (EmD) across three generations is unclear. The present study addressed this in a sample of 284 families participating in the Oregon Adolescent Depression Project. Structured clinical interviews were used to collect psychiatric history data on a community cohort of G2 individuals and their G1 parents. G2 parents rated EmD symptoms in their G3 children (M age=5 years, SD=2.4). Results indicated that G1 SUD was associated with increased risk of G3 EmD symptom elevations, above and beyond the influence of comorbid G1 EmD. G2 SUD was associated with a similar independent increase in risk for G3 EmD symptoms. Also, G1 SUD conferred risk for G2 SUD. Mediational tests indicated that the influence of G1 SUD on G3 EmD was transmitted via its influence on G2 SUD. G1 and G2 SUD did not interact in predicting G3 EmD; rather results suggested an additive influence. There was no evidence that the influence of G1 SUD on G3 EmD was transmitted via G2 EmD. These findings shed light on the multigenerational processes through which SUD influences EmD.

Selective effects of benzodiazepines on the acquisition of conditioned taste aversion compared to attenuation of neophobia in C57BL/6 mice

INTRODUCTION

The effects of pre-conditioning administration of anxiolytic benzodiazepines on the acquisition of a conditioned taste aversion (CTA) and on the acquisition of attenuation of neophobia (AN) were investigated in C57BL/6 mice.

MATERIALS AND METHODS

A CTA was induced by injecting lithium chloride (LiCl; 6 mEq x kg(-1)) 30 min after the animal had imbibed a novel 0.5% saccharin solution. In other animals, neophobia was attenuated by a single access to the novel 0.5% saccharin solution, followed only by injection of saline.

RESULTS AND DISCUSSION

Pre-conditioning administration of chlordiazepoxide (CDZ; 6-24 mg x kg(-1), i.p.) and alprazolam (0.3-1 mg x kg(-1), p.o.) resulted in a CTA that did not differ initially from that observed in vehicle-treated controls, but which showed faster extinction. The acquisition of AN was impaired only after the higher doses of CDZ (12-24 mg x kg(-1), i.p.) or alprazolam (1 mg x kg(-1), i.p.). The results show that in this test, altered acquisition of an aversive CTA memory by anxiolytic benzodiazepines is reflected in more rapid extinction. Moreover, at low doses, these drugs showed selectivity for weakening CTA learning compared to AN learning. Evidence is discussed that selective weakening of aversive memory formation is a clinically relevant effect of anxiolytic benzodiazepines.

Differential familial liability of panic disorder and agoraphobia

To examine the familial liability of panic disorder (PD) and agoraphobia (AG) in a community sample, namely the effect of parental PD and AG on the offspring's risk to develop either or both conditions in adolescence or adulthood. A representative community sample of N=3,021 adolescents and young adults aged 14-24 years at baseline was followed up over a period of 10 years in up to four waves. Family information was assessed by either direct interviews with at least one parent or by using subjects' family history information at either wave (N=3,014). Diagnoses and selected symptoms were assessed in both, parents and subjects, by using a standardized diagnostic interview (DSM-IV M-CIDI) with its respective family history module. (1) Parental panic attacks (PA), PD, and AG were all shown to be associated with an increased risk of offspring to also develop PA, PD, and AG. (2) Associations of parental PD were present irrespective of parental AG, whereas parental AG without PD was not associated with an increased offspring risk. (3) Outcome risk was particularly elevated in offspring of parents with PD+AG. (4) Parental PD or AG was not associated with an earlier age of onset of any syndrome in the offspring. We confirmed and expanded previous results from clinical samples that comorbid PD and AG aggregate in families. AG without PD is not familial, but it might enhance the familial transmission of PD.

Specificity of familial transmission of anxiety and comorbid disorders

This study examines the specificity and impact of comorbid disorders in probands on the familial transmission of panic and social anxiety disorders. It employs a contemporary family study design with 225 probands (with and without panic and social anxiety disorders) sampled from outpatient clinics and the local community. Their 1053 adult first-degree relatives were assessed for lifetime disorders, based on best estimate diagnoses derived from semi-structured psychiatric diagnostic interviews (Schedule for Affective Disorders and Schizophrenia), multi-informant family history information, and medical records. Generalized estimating equations were used to examine the familial aggregation of panic and social anxiety disorders, and the contributions of comorbid disorders. Results show specificity of familial aggregation of both panic disorder and social anxiety in probands and relatives (i.e., panic odds ratio=3.7, 95%CI 1.5-9.3; social anxiety odds ratio=1.8, 95%CI 1.1-2.9) after controlling for comorbid disorders. There was no contribution of common comorbid disorders (depression, alcoholism, generalized anxiety disorder and agoraphobia) in probands on the familial aggregation of either disorder. These findings confirm prior studies of specificity of familial transmission of panic and social anxiety disorders, and demonstrate that the association between these disorders in probands is not attributable to comorbid mood, anxiety or substance use disorders. Therefore, despite the high magnitude of co-occurrence of panic disorder and social anxiety, there may be distinct etiologic factors underlying each disorder. These findings have implications for studies of the etiology, genetics, and treatment of these disorders.

Effects of social crowding on emotionality and expression of hippocampal nociceptin/orphanin FQ system transcripts in mice

The novel nociceptin/orphanin FQ (N/OFQ) system was proposed to be an important component of neural circuits involved in stress-coping behaviour and fear. This study investigated whether variations between the mouse strains in vulnerability to social crowding stress might be linked to different regulation of N/OFQ system transcripts in mice. Three weeks old C57BL/6J (B6), BALB/cByJ (CBy) and 129S2/SvPas (129S2) male mice were housed individually or in crowded (7/cage) conditions and then tested as adults in a battery of anxiety tests (open field, elevated plus-maze and acoustic startle reflex tests). Both 129S2 and B6 mice displayed increased signs of anxiety under crowded housing, while CBy mice tended to show the opposite profile. Analysis of gene expression revealed a 10-fold increase of nociceptin precursor and 4-fold increase of the NOP receptor mRNAs contents in the hippocampus of CBy mice kept in crowded conditions compared to those housed individually. In B6 mice, mRNA level of the peptide precursor remained unchanged, while that of the receptor was increased by 2-fold under crowding compared to individual housing. No significant changes were detected in 129S2 mice. These findings show that social housing may be important environmental stress factor in mice depending on the strain. The possible involvement of central nociceptin mechanisms in behavioural resilience to social crowding stress is discussed.

Update on psychiatric genetics

Genetic factors play a fundamental role in the genesis of many mental disorders. The identification of the underlying genetic variation will therefore transform parts of psychiatry toward a neuroscience-based discipline. With the sequence of the human genome now available, the majority of common variations identified, and new high-throughput technologies arriving in academic research laboratories, the identification of genes is expected to explain a large proportion of the risk of developing mental disorders. So far, a number of risk genes have been identified, but no major gene has emerged. The majority of these genes participate in the regulation of biogenic amines that play critical roles in affect modulation and reward systems. The identification of genetic variations associated with mental disorders should provide an approach to evaluate risk for mental disorders, adjust pharmacotherapy on the individual level, and even allow for preventive interactions. New targets for the development of treatment are anticipated to derive from results of genetic studies. In this review, we summarize the current state of psychiatric genetics, underscore current discussions, and predict where the field is expected to move in the near future.