In the article “A longitudinal, Genetically Informative, Study of Associations Between Anxiety Sensitivity, Anxiety and Depression”, the authors Zavos, Rijsdijk and Eley examine the direction of effects between anxiety sensitivity and anxiety, anxiety sensitivity and depression and anxiety and depression as well as the influences of heredity and environment through the development of adolescents. Based on previous theories, the authors expected to find a bidirectional relationship between anxiety sensitivity and anxiety and a predictive factor of anxiety sensitivity in regards to depression. Also, they expected to find that environmental influences are time sensitive whereas genetic factors are more stable through time. In preparation and guidance for this study, the authors reviewed several other studies focusing on the direction on influence and correlative representativeness of anxiety sensitivity, anxiety and depression. It was previously found in a majority of studies, that anxiety preceeds depression but it was very unclear of whether or not depression predicts anxiety sensitivity. Several studies also showed that anxiety sensitivity explains variance in anxiety as unrelated to trait anxiety. In regards to heredity and environmental factors, genetic factors were shown to contribute more towards the stability of symptoms over time and environmental factors were shown to be responsible for change. For this study, data from the G1219 study, which is a longitudinal study of 3640 adolescent twins and siblings from the ages of 12-29 years, was used. The sample consisted of 168 monozygotic male, 199 monozygotic female, 138 dizygotic male and 190 dizygotic female candidates. Zygosity was established through a questionnaire answered by the mothers of the candidates. The authors compared the education levels and housing tenure of the parents with a large nationally representative sample of parents. They found that the parents of the participants were more likely to own their own homes and have somewhat higher levels of education than the sample. Predictors of decline in response were also measures between the waves of data collection. These included the sex of the child as responses were more likely from girls; housing tenure as responses were more likely from parents whom owned their own home; and parental education as responses were more likely from participants with parents with a higher degree of education. The participating families were thus weighted according to the inverse of their probability of participation.
The average age of the participants was 15 years at time one and 17 years at time two. Informed consent was obtained from parents/ guardians of all participants under the age of 16, and from the adolescents themselves when age 16 or over. The authors obtained ethical approval for the different stages of the study from the Research Ethics Committees of the Institute of Psychiatry, South London and Maudsley NHS Trust and Goldsmiths, University of London.
The authors used a correlational, field based design in conducting their research and measurements. For measurement of anxiety sensitivity, the Child Anxiety Sensitivity Index, which is a 16-item questionnaire that measures children’s sensitivity to different measures of anxiety, was used. For anxiety, the Spence Children’s Anxiety Scale was used. This is a 38 item self-reporting questionnaire that measures anxiety disorder symptoms in children and is measured on a four point scale. For measuring depression, the Short Mood and Feelings Questionnaire that is also self-reporting and consists of 13 items which assess the core depressive symptoms that occur over the previous two week period, was used.
The statistical results of the study showed that females rated their levels of all three categories higher than males at both times of data collection but the scores on all three scales decreased over time for both males and females. Correlations between anxiety and both anxiety sensitivity and depression were high at both times of data collection and there was only a moderate correlation between anxiety sensitivity and depression at both times as well. Hence, the authors demonstrated that there is stability in the symptoms of anxiety sensitivity, anxiety and depression throughout adolescence and reciprocal associations between the variables were evident. Genetic affects were found to be most important in explaining the stability of the relationships over time though time specific genetic effects were also substantial. Non-shared environmental influences were more time specific, with little correlation between data collections.
After reviewing the research, I believe that a few limitations should be noted. First, the analysis were conducted on data collected from questionnaires which may fail to capture some of the complexities of the phenotypes in question and there was also evidence of selection bias. Additionally, there were large age ranges at each wave which makes it hard to attribute emergence of developmental influences to specific ages. Other limitations that should be noted is that eh sample consisted of primarily twins and the assumption that causal processes influencing variables do not change over the time period. Overall, I thought that the authors took all of these limitations into account in some way or another. I also thought that they organized the article very well and were very clear in their summation of the previous research. The article was easy to read and each topic was clearly defined and explained as they went along.
For application purposes, this study clearly shows that heredity plays an enormous factor in the development of anxiety and depression. Thus, teachers, day care providers and parents/ guardians should pay close attention to symptoms children may be showing if there is a history of such disorders within the family. Teachers, day care providers and parents/ guardians should also pay close attention to other correlating symptoms if a child shows symptoms of one disorder, as the authors also showed that there is a higher likelihood of both occurring at the same time as well as anxiety sensitivity.
If I were to be conducting this research, I would ask the question of whether or not social implications impact the development of anxiety and depression throughout adolescence. I would take into account the genetic factors as predispositions of the likeliness of the disorders to occur but I would have also taken into account social factors that may impact the development of the disorders. For instance, I would attempt to explore if there is a correlation between children coping with obesity, as it is shown that children with obesity are less likely to perform well and like school, who are genetically predispositioned to develop anxiety and those who are not. I would also take into consideration other social impacts such as number of friends, participation in extracurricular activities and so forth. I believe that these social influences would have a large impact on whether or not a child develops anxiety and/or depression especially if they are genetically predispositioned. I would also like to explore whether or not family influences have an effect on the development of the disorders. For example, does being raised in a very religious house lower the chances of developing the disorders, does being raised in a household where both parents work full time impact the development, and does the closeness of extended family have an impact on the development of anxiety and/or depression.