The purpose of the present dissertation was to evaluate the internal validity of symptoms of four common anxiety disorders included in the Diagnostic and Statistical Manual of Mental Disorders fourth edition (text revision) (DSM-IV-TR; American Psychiatric Association, 2000), namely, separation anxiety disorder (SAD), social phobia (SOP), specific phobia (SP), and generalized anxiety disorder (GAD), in a sample of 625 youth (ages 6 to 17 years) referred to an anxiety disorders clinic and 479 parents. Confirmatory factor analyses (CFAs) were conducted on the dichotomous items of the SAD, SOP, SP, and GAD sections of the youth and parent versions of the Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV: C/P; Silverman & Albano, 1996) to test and compare a number of factor models including a factor model based on the DSM. Contrary to predictions, findings from CFAs showed that a correlated model with five factors of SAD, SOP, SP, GAD worry, and GAD somatic distress, provided the best fit of the youth data as well as the parent data. Multiple group CFAs supported the metric invariance of the correlated five factor model across boys and girls. Thus, the present study’s finding supports the internal validity of DSM-IV SAD, SOP, and SP, but raises doubt regarding the internal validity of GAD.

This qualitative focus groups analysis examines the harmful effects of violent video games on emotions and behavior by comparing violent video game player's responses to that of non-violent video game players of the same age group. Research on the effects of video games has been done since the 70s, yet more research is needed to better understand the potentially harmful emotional and behavioral effects of playing violent games, especially from the gamers' perspectives. This thesis presents a qualitative analysis of data obtained from focus group sessions among undergraduate college students. Results of the analysis supports the presence as well as absence of violent video game effects, according to violent and non-violent video gamers' personal experiences and in their own words.

Background: Response bias can distort treatment effect estimates and inferences in clinical trials. Although prevention, quantification, and adjustments have been developed, current methods are not applicable when subject-level reliability is used as the measure of response bias. Thus, the objective of the current study is to develop, test, and recommend a series of bias correction strategies for use in these cases. Methods: Monte Carlo simulation and logistic regression modeling were used to develop the strategies, examining the collective impact of sample size (N), effect size (ES), reliability distribution, and response style on estimating the treatment effect size in a series of hypothetical clinical trials. The strategies included a linear (LW), quadratic (QW), or cubic weight (CW) applied to the subject-level reliability; a reliability threshold (%); or a combination of the two (W-%). Bias and percent relative root mean square error (RRMSE (%)) were calculated for each treatment effect estimate and RRMSE (%) was compared to inform the bias correction recommendations. Results: The following recommendations are made for each N and ES combination: N=200/ES=small: no adjustment, N=200/ES=medium: 40%-LW, N=200/ES=large: 40%-QW, N=2000/ES=small: 40%-LW, N=2000/ES=medium: 55%-CW, N=2000/ES=large: 75%-CW, N=20000/ES=small: 70%-CW, N=20000/ES=medium: 85%-CW, N=20000/ES=large: 95%-CW. Conclusion: Employing these bias correction strategies in clinical trials where subject-level reliability can be calculated will decrease error and increase accuracy of estimates and validity of inferences.

Sweden’s drug policy still invokes the ideas of zero-tolerance and prohibition despite the high reported number of drug-related deaths and arrest rates for using drugs in Sweden in the latest years. To reach knowledge about why prohibition of illegal drugs has remained such a strong staple of Swedish politics for the latest 60 years, this study asks questions about which ideas and arguments constituting the Swedish drug policy, examines the logical coherence of these, and proposes an alternative policy route which aims to mitigate the shortcomings of the current policy. The drug policy field is extensive and studies from different nations show that drug policies that move away from prohibitionist ideas have succeeded in both reducing drug-related mortality rates and reducing the stigma that is attached to either using or abusing psychoactive drugs. Because of an identified unclarity of why the prohibitionary ideas in Sweden have remained despite recent developments, this study aims to fill a gap in existing research by normatively analyzing the ideas in the policy. Since these ideas have great importance in restrictions of individual liberty and public health considerations, knowledge about them is essential to create because liberty and public health are fundamental aspects in any democratic society. The research endeavor performs an internal validity check as the methodological approach to check the internal logic and arguments of the policy and uses a theory of liberty to shed light on the trade-offs between liberty and public health. What is discovered is that the Swedish drug policy builds on inconsistent arguments and incoherent logic and has a moralizing intent that allows for restrictions on individual liberty to reach a utopian vision of a drug-free society. Also, this study shows that it is possible to create a policy that can mitigate the harms caused by the current by adhering to the principle that individual liberty should stretch as far as possible when no harm is caused to another. The implications of this are that it will be harder to justify the zero-tolerance approach in the future and that future policy must look to other policy approaches rather than build policy on assumptions based on outdated moralism.