BMC by Annalijn I. Conklin and Christopher G. Richardson 16 July 2018
Depression is a common psychological disorder that affects 121 million people worldwide and is the leading cause of disability when measured by years lived with disability (YLDs). Rising rates of depression diagnoses among youth, with about 20% experiencing depression before adulthood, have led many counties to prioritize initiatives that enhance prevention, early identification, and treatment efforts.
Depression causes persistent feelings of sadness and loss of interest in activities of daily living, impacting overall health and wellbeing. The common misinterpretation of depressed states as transient “normal” phases of adolescence combined with widespread stigma have contributed to the current situation where the vast majority of depressed youth are not being treated.
The development of depression among youth can lead to substance (mis)use, decreased quality of life and suicide. Furthermore, young people who experience depression are also at increased risk of having poor health and economic outcomes in adulthood.
Factors that increase the risk of depression in young people include abuse and neglect, chronic physical illness, family history of mental illness, other mental health problems and the experience of stressful life events. It has also been found that female youth develop depression twice as often as young men, although some of this difference is due to the way researchers ask questions when determining symptoms of depression.
But what about sleep?
Sleep is essential for health and proper sleep for young people is critical for proper growth and it it is recommended that young people aged 13-18 years sleep 8 to 10 hours per night. Yet, getting enough sleep is not commonly talked about as a potential determinant of youth depression.
Adolescence is a critical period of development that is marked by substantial reductions to slow wave and rapid eye movement sleep, increases in sleep disturbance, a circadian shift to an evening chronotype and a shortening of total duration of sleep. These neuro-endocrine changes often lead to young people lacking adequate amounts of total sleep. negative consequences of sleep deprivation include mood disturbances, poor academic performance, weight gain, increased food intake, substance use and other poor health behaviors.
The relationship between short sleep (i.e. poor quantity) and depression in young people has not been well studied. Although some investigators have used prospective study designs that allow for some inference about causality, the majority of work in this area involves cross-sectional designs which measure both sleep deprivation and depression at the same point in time so there is no way to know if disrupted sleep precedes the emergence of depression.
Even the studies that are somewhat better designed to assess causality frequently measure sleep problems only once and then follow people over time to identify risk of developing depression. Although not conclusive, the results of these types of studies suggest that short sleep duration precedes depression in young people but not the reverse.
None of the existing studies look at gender differences despite the fact that women and men are known to differ in the developmental course of depression, and they also experience distinct risk factors that are known to influence depression because of their biology and social status.
We wanted to fill this gap in evidence using data that was collected multiple times from a large group of young people in British Columbia (BC), Canada. We used answers that young people gave to questions about their sleep and awake times to determine whether they were sleep deprived and we calculated this at three time points, roughly 6 months apart.
This design allowed us to determine the extent to which they were chronically sleep deprived. We used this information to study the cumulative effect of chronic sleep deprivation (compared to occasional or no history of sleep deprivation) on the risk of depression from a gender perspective.
Our hypothesis was that chronic sleep deprivation, defined as less than 8 hours per weeknight, would be linked to higher depression levels, and that the relationship would vary between young women and young men.
Our results showed that cumulative sleep deprivation in young women was linked to higher depression scores at the study follow-up, but there was no clear relationship among young men. The size of the effect we found was initially medium when we used simple statistical models of the relationship; however, it was smaller when we also accounted for a number of the factors that are known to influence both depression and sleep.
Our work adds new evidence on the role of repeated sleep deprivation in young people on their risk of depression and how the effect differs by gender. We believe this is an important area of research that needs more attention, both in terms of thinking about these relationships and in terms of measuring them in a rigorous way.
We think it is important for young women to be supported in achieving the recommended amount of sleep as a potentially important way of promoting mental health among young people.
Annalijn I. Conklin is a Scientist, Centre for Health Evaluation and Outcome Sciences, Providence Healthcare Research Institute, and an Assistant Professor in the Faculty of Pharmaceutical Sciences at the University of British Columbia.