| 1. |
- Langenskiöld, Sophie
(författare)
-
Peer influence on smoking : causation or correlation?
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we explore two different approaches to causal inferences. The traditional approach models the theoretical relationship between the outcome variables and their explanatory variables, i.e., the science, at the same time as the systematic differences between treated and control subjects are modeled, i.e., the assignment mechanism. The alternative approach, based on Rubin's Causal Model (RCM), makes it possible to model the science and the assignment mechanism separately in a two-step procedure. In the first step, no outcome variables are used when the assignment mechanism is modeled, the treated students are matched with similar control students using this mechanism, and the models for the science are determined. Outcome variables are only used in the second step when these pre-specified models for the science are fitted. In the first paper, we use the traditional approach to evaluate whether a husband is more prone to quit smoking when his wife quits smoking than he would have been had his wife not quit. We find evidence that this is the case, but that our analysis must rely on restrictive assumptions. In the subsequent two papers, we use the alternative RCM approach to evaluate if a Harvard freshman who does not smoke (observed potential outcome) is more prone to start smoking when he shares a suite with at least one smoker, than he would have been had he shared a suite with only smokers (missing potential outcomes). We do not find evidence that this is the case, and the small and insignificant treatment effect is robust against various assumptions that we make regarding covariate adjustments and missing potential outcomes. In contrast, we do find such evidence when we use the traditional approach previously used in the literature to evaluate peer effects relating to smoking, but the treatment effect is not robust against the assumptions that we make regarding covariate adjustments. These contrasting results in the two latter papers allow us to conclude that there are a number of advantages with the alternative RCM approach over the traditional approaches previously used to evaluate peer effects relating to smoking. Because the RCM does not use the outcome variables when the assignment mechanism is modeled, it can be re-fit repeatedly without biasing the models for the science. The assignment mechanism can then often be modeled to fit the data better and, because the models for the science can consequently better control for the assignment mechanism, they can be fit with less restrictive assumptions. Moreover, because the RCM models two distinct processes separately, the implications of the assumptions that are made on these processes become more transparent. Finally, the RCM can derive the two potential outcomes needed for drawing causal inferences explicitly, which enhances the transparency of the assumptions made with regard to the missing potential outcomes.
|
|
| 2. |
- Ssegonja, Richard
(författare)
-
Effectiveness and cost-effectiveness of indicated preventive interventions for depression in adolescents : An application of health economics methods
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Unipolar depressive disorders are commonly encountered conditions in clinical practice with about 25% reporting their first episode during adolescence. Longitudinal studies show adolescent depression to be associated with an increased risk of mental illness in adulthood, healthcare usage, poor educational outcomes, unemployment, and dependency on welfare recipiency. Therefore, adolescent depression contributes a high disease burden and impinges a considerable financial strain on society’s limited resources.Several preventive interventions have been developed to prevent adolescent depression. Of these interventions, group-based cognitive behavioural therapy (GB-CBT) indicated preventive interventions for depression are well studied and accepted. However, evaluations of their effectiveness and cost effectiveness have yielded conflicting and incomplete results mainly due to methodological limitations.Therefore, the overarching aim of this thesis was to investigate the effectiveness and cost-effectiveness of GB-CBT indicated preventive interventions for depression in children and adolescents, and estimate the additional healthcare costs and welfare burden in early to mid-adulthood associated with adolescent depression.In study I, GB-CBT indicated preventive interventions for depression in children and adolescents were protective against developing a depressive disorder and also reduced depressive symptoms. The intervention relative effect was noted to decay over time. Study II revealed that adolescent depression was associated with considerable increased healthcare consumption in mid-adulthood compared to the non-depressed peers at a population level. This finding was more pronounced in females with persistent depressive disorder (PDD). Study III showed adolescent depression to be associated with all the forms of social transfer payments (welfare) especially in individuals with PDD and those with early comorbid psychopathologies.Study IV demonstrated that GB-CBT indicated preventive interventions for adolescent depression are not only effective but also have the potential to be cost-effective compared to leaving adolescents with subsyndromal depression unattended.Findings from studies II and III, emphasized the large financial burden to society in terms of additional healthcare costs and welfare expenditure associated with adolescent depression. Whereas, study I and IV bring forward the message that it is possible to change the course of subsyndromal depression by offering GB-CBT indicated preventive interventions to adolescents with subsyndromal depression. Such an initiative was not only cost-effective compared to not intervening, but also largely cost-saving. Therefore, GB-CBT indicated preventive interventions could be used as part of a stepped care program linking into more specialized care services. The results of this thesis will be useful in decision-making concerning the resource allocation related to adoption and implementation of such preventive measures.
|
|
| 3. |
- Viberg Johansson, Jennifer, 1982-
(författare)
-
INDIVIDUAL GENETIC RESEARCH RESULTS : Uncertainties, Conceptions, and Preferences
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contributes to the ethical discussion on how to handle incidental findings in biomedical research using sequencing technologies from a theoretical and an empirical perspective. Study I and II are theoretical studies that used conceptual analysis. Study I demonstrates that the argument for disclosure based on the principle of beneficence ignores the complexity and uncertain predictive value of genetic risk information. The argument neglects the distinction between an incidentally discovered disease and an incidentally discovered risk for disease with unclear predictive value. Study II investigates the proposal to let participants express their preferences to incidental genetic findings in the consent form. The study argues that this freedom of choice is problematic because it is uncertain whether the opportunity to choose in the consent phase enables people to express what they truly prefer. Participants might be steered to a specific answer depending on mood, triggered feelings, and the framing of the question.The second part of the thesis is empirical and used both a qualitative and a quantitative approach. Study III investigates research participants’ understanding of genetic risk and used a phenomenographic approach and focus group interviews. One result was that participants understood genetic risk in binary terms. This understanding involved an either/or concept of genetic risk. Participants tend not to understand genetic risk as a probability. They also interpreted the information in terms of their past, present, and future life. Study IV used a questionnaire with a stated preference technique called Discrete Choice Experiments (DCE) to investigate participants’ preferences for genetic risk information. An effective preventive measure was the most important characteristic for research participants in their decision to be given genetic risk information. When the disease was life threatening, had a high penetrance probability, and had effective preventive measures, 98% of the participants wanted to know their incidental genetic risk information.As genetic risk information has many different characteristics and includes many uncertainties, ethical discussions and empirical studies of people’s attitudes and preferences need to explicitly engage the complexity of genetic incidental findings.
|
|
