Disclosure of personal information is believed to be more frequent in online compared to offline communication. However, this assumption is both theoretically and empirically contested. This systematic review examined existing research comparing online and offline self-disclosure to ascertain the evidence for current theories of online communication. Studies that compared online and offline disclosures in dyadic interactions were included for review. Contrary to expectations, disclosure was not consistently found to be greater in online contexts. Factors such as the relationship between the communicators, the specific mode of communication, and the context of the interaction appear to moderate the degree of disclosure. In relation to the theories of online communication, there is support for each theory. It is argued that the overlapping predictions of each theory and the current state of empirical research highlights a need for an overarching theory of communication that can account for disclosure in both online and offline interactions.

Short (≤6 hours) and long (>9 hours) sleep durations are risk factors for mortality and morbidity. To investigate whether the prevalences of short and long sleep durations have increased from the 1970s to the 2000s, we analyzed data from repeated cross-sectional surveys of 10 industrialized countries (38 nationally representative time-use surveys; n = 328,018 adults). Logistic regression models for each country were used to determine changes in the prevalence of short and long sleep durations over time, controlling for sampling differences in gender, age, number of weekend days included, and season of data collection. Over the periods covered by data, the prevalence of short sleep duration increased in Italy (adjusted odds ratio = 2.64, 95% confidence interval (CI): 2.41, 2.89) and Norway (adjusted odds ratio = 2.33, 95% CI: 1.77, 3.08) but decreased in Sweden, the United Kingdom, and the United States. The prevalence of long sleep duration increased in Australia (adjusted odds ratio = 1.14, 95% CI: 1.05, 1.25), Finland (adjusted odds ratio = 1.30, 95% CI: 1.14, 1.48), Sweden (adjusted odds ratio = 1.51, 95% CI: 1.35, 1.69), the United Kingdom (adjusted odds ratio = 2.03, 95% CI: 1.68, 2.46), and the United States (adjusted odds ratio = 1.50, 95% CI: 1.36, 1.65) but decreased in Canada and Italy. No changes were observed in Germany or the Netherlands. Limited increases in short sleep duration challenge the claim of increasingly sleep-deprived societies. Long sleep duration is more widespread than is short sleep duration. It has become more prevalent and thus should not be overlooked as a potential contributor to ill health.