The constructs of interest are conceptualized as variables in this study, which is another strength; the researchers sought out to find the effects of insomnia on professional life, and they studied good sleepers in comparison to those with insomnia, and they studied the effects of sleep on professional life and medical health in relation to their careers. One weakness is that there is not a critical test in the articles that tests two opposing theories; while this is not necessary for all strong studies, it would have strengthened the. For example, they could have studied insomnia theory, which allows for the problems in sleeping to effect daily life. This could have been compared to sleep deprivation theory which, while similar, it states that long term sleep deprivation studies show that participants do not have as much difficulty in everyday life as do those deprived of sleep on a short term basis. There do not seem to be conceivable limitations of the study, and therefore this study’s results seem valid.   

	Overland did a historical cohort study related to the topic of socioeconomic factors. They sought to study insomnia and depression, and how the disorders predict disability pension. It was found that insomnia and depression were both predictors of disability pension at similar rates. There was also a higher rate of somatic disorders for  participants who had insomnia alone (without depression). The mentioned associations were stronger for those under the age of 45. And insomnia was related to more work-related types of disabilities than was depression. These results imply that there is a predictive aspect to insomnia, which is that in addition to health risks insomnia can ultimately result in the need for financially assisted living. 

	Seemingly, the only weakness of this study was the limitation that the “non-attendees” were unable to provide an adequate amount of data; this is important because the non-attendees seemed to have higher rates of disability pension award as well as higher rates of illnesses . Otherwise, this study showed many strengths: The theoretical propositions of past research were explored and a new approach of comparisons of theoretically comorbid factors were studied. These results added to future research and especially added to the knowledge of socioeconomic factors related to insomnia.

	A study of New Zealand’s Maori and non-Maori populations researched the links between the symptoms of insomnia, ethnicity, gender, age, employment status, and socioeconomic deprivation. Population prevalence information was considered and self-reports of insomnia symptoms were recorded by the experimenters. The findings of this study showed that the Maori participants reported more sleeping problems and insomnia symptoms. There was a strong association between unemployment and socioeconomic deprivation with insomnia as well as with sleep problems that lasted longer than 6 months. The focus of the authors was to look at health inequalities in New Zealand, and the results indicated that there are health inequalities which are based on socioeconomic deprivation.
