Anxiety comprises many clinical descriptions and pheno-types. A genetic predisposition to anxiety is undoubted;however, the nature and extent of that contribution is stillunclear. Methods for the genetic analysis of such complexdisorders is briefly reviewed, followed by a discussion ofthe comorbidity of anxiety with other psychiatric disordersand their possible common genetic etiology. Extensivegenetic studies of the serotonin (5-hydroxytryptamine,5-HT) transporter (5-HTT) gene have revealed how varia-tion in gene expression can be correlated with anxietyphenotypes. Complete genome-wide linkage scans forpanic disorder (PD) susceptibility genes have suggested alocus on chromosome arm 7p, and association studies havehighlighted many candidate genes. A highly significantassociation between phobias, panic disorder, and a dupli-cation at chromosomal region 15q24-26 is one of the mostexciting findings to date. Emerging molecular genetictechnologies and the use of increasingly sophisticatedanimal models of anxiety provide great promise for thefuture of the field. Dialogues Clin Neurosci. 2002;4:251-260.nxiety is part of the normal human experience.We may speculate that it served human survival duringevolution by enhancing preparedness and alertness.However, anxious manifestations are abnormal whenthey are exaggerated in excess of any objective dangerthat the individual is facing, when they induce psycho-logical distress or physical ailments, or when they areself-aggravating in a vicious circle.As a subject of clinicaldiagnosis, anxiety may be chronic, for instance, in sometypes of personality disorder or in generalized anxietydisorder (GAD); in such cases, it is akin to a “trait.” Inother instances, anxiety is a short-lived, noncontinuous,discrete symptom, for example, in panic disorder (PD)or in acute stress; then it is a “state,” rather than a trait.Anxiety comprises many phenotypes and clinicaldescriptions. It is routinely partitioned into disorders ofgeneral anxiety, panic, phobia, and in some classifica-tions, obsessive-compulsive disorder (OCD); and thelifetime prevalence for the group of disorders has beenestimated to be as high as 25%.1 Even this classificationdoes not go far to encompass the complexity of anxiety,and hence the arduousness of the task of getting at itsbiological root. The success to date has not been over-whelming; however, some recent studies have providedmore hope than was in the past thought to be realistic.OCD is sometimes classified with anxiety (eg, in theDiagnostic and Statistical Manual of Mental Disorders[DSM]) and sometimes not (eg, in the InternationalStatistical Classification of Diseases, 10th Revision [ICD-10]). Attempts to unravel the genetics of OCD arenumerous and would be best served in a treatise of theirown, and so will not be included in this review. Sincemany genetic studies on anxiety have been performedB a s i c r e s e a r c h2 5 1Are there anxious genes?Deborah J. Morris-Rosendahl, PhDAKeywords: anxiety, anxiety disorders, panic disorder, geneticsAuthor affiliations: Institute for Human Genetics and Anthropology, AlbertLudwigs University of Freiburg, Freiburg, GermanyAddress for correspondence: Deborah J. Morris-Rosendahl, PhD, Institutfür Humangenetik und Anthropologie, Albert Ludwigs UniversitätFreiburg, Breisacherstr 33, D-79106 Freiburg, Germany(e-mail: morrisro@ukl.uni-freiburg.de)
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