Background: Imprecision of the psychiatric phenotype might partially explain the failure of genetic research to identify genes that contribute to susceptibility of anxiety disorders. It has been suggested that using a broad anxiety phenotype instead of a DSM-IV anxiety disorder diagnosis might enhance the chance of finding candidate genes for this complex group of symptoms. Previous research concluded that two underlying constructs, worry and rumination may explain anxiety subsyndromic symptoms in Costa Rican patients with history of mania or hypomania. Therefore, the goal of the current study is to explore the presence of latent constructs for quantitative anxiety in a group of subjects with a wide diagnostic phenotype (schizophrenia, schizoaffective disorder, bipolar disorder and major depressive disorder) and non-affected individuals.
Methods: We conducted an exploratory factor analysis of anxiety trait in 709 subjects originally recruited for a Costa Rican study of Bipolar Disorder. Our sample was comprised by 419 (59%) subjects with psychiatric disorders and 290 (41%) non-affected individuals. The most frequent diagnoses were bipolar disorder 167 (23%) followed by major depressive disorder 144 (20%). The sample was 57% female and had a mean age of 41.2 (SD 14.90). We used principal factors extraction method with squared multiple correlations (SPSS v.20) of the STAI (trait subscale).
Results: A three-factor solution with a good simple structure and statistical adequacy was obtained with a KMO of 0.92 (>0.6) and Bartlett's Test of Sphericity of 5644,44 (p<0.05). The STAI items were grouped into three factors: 1) anxiety-absent, 2) worry and 3) rumination based on the characteristics of the symptoms.
Discussion: Two underlying constructs, worry and rumination may explain anxiety subsyndromic symptoms in Costa Rican subjects. Responses to items associated with factor 1 describe people with emotional stability, meaning no anxiety. The items associated to the factor 2 indicate anxiety about actual and future events and stressful situations, meaning worry. On the other hand, the factor 3 cluster components associated with thoughts about past events and recurrent situations, namely rumination. How the type of symptoms affects the clinical presentation and prognosis of the mania/hypomania raise an important line of research. Our proposed underlying structure of subsyndromal anxiety in individuals should be considered as an important factor in defining better phenotypic characterizations on a broader diagnostic concept. Worry and rumination as a phenotypic characterization may assist in genotyping; however, its predictive value on actual illness outcome still requires more research. The Genome-Wide QTL analysis for anxiety trait in the same sample is ongoing.