A new study led by University of Ottawa researchers uncovered how chronic sleep disruption during adolescence can make individuals far more susceptible to developing depression than they otherwise might be.

The study, published in November in Behavioral Brain Research, examined the impact of persistent sleep disruption on stress reactivity, using a mouse model to do so. Researchers used 80 adolescent and adult mice, split evenly between males and females, which were manually sleep disrupted for eight consecutive days and then exposed to a stressor in order to determine depression-like behavior. A control group was allowed normal rest for the same time period.

The findings determined that both adolescent male and female mice displayed a higher amount of depression-like behavior after the week of interrupted sleep, while the adult mice did not.

The researchers decided to delve into the topic of adolescent sleep disruption and how it can relate to the onset of depression due to how most adult cases of depression in humans generally begin during adolescence, according to Nafissa Ismail, an associate professor at the University of Ottawa School of Psychology and senior writer on the study.

“Depression during adolescence is often treatment-resistant,” Ismail said. “Since mental health has been challenging to treat, my team and I decided to work on the prevention aspect and understand the various factors that can increase an individual’s likelihood of developing depression. Adolescent development often includes a delay in sleep/wake schedule.”

Ismail added that in the beginning of adolescence, a person’s sleep schedule has an early onset of sleep, while sleep onset in mid- and late adolescence becomes delayed and begins to resemble an adult sleep schedule.

“Adolescent sleep delay is further exacerbated by ‘social jet lag’ or the discrepancy between biological rhythm and reduced social constraints to conform to a regular sleep pattern on non-work/school days,” Ismail said. “So, we wondered whether chronic sleep disruptions in adolescents could increase their vulnerability to mental health conditions like depression.”

The research also highlighted that female mice had a higher level of stress hormone release than their male counterparts, making them even more reactive to stressors.

“Females tend to be more reactive to stress in general. So exposure to the same stressor will typically induce greater levels of corticosterone in females than in males,” Ismail said. “However, following chronic sleep disruption, there is a sensitization of the stress response in females, making them even more reactive to stress compared to their male counterparts.”

Ismail noted that the research team would like to examine the impact of chronic sleep disruption in humans, though the ability to carry out such a study is made difficult due to individual factors — such as a person’s general level of preexisting stress, their environment, or overall personality — that cannot be controlled. As such, it would be more difficult to draw a strong conclusion with human study subjects, Ismail said.

The study ultimately found that “adequate sleep is necessary to the prevention of depression because significant sleep delays during adolescence increase the likelihood of depression onset in both males and females,” Ismail said. She also added that the progression of the COVID-19 pandemic may amplify the relationship between poor sleep and mental health disorders.

“We all know that the current pandemic has disrupted the sleep of many, but it has especially disrupted the sleep of our adolescents, and this could place adolescents at a higher risk than ever before for developing depression and other mood disorders,” Ismail said.

The study, titled “Chronic sleep disruption induces depression-like behavior in adolescent male and female mice and sensitization of the hypothalamic-pituitary-adrenal axis in adolescent female mice,” was published Nov. 13 in Behavioral Brain Research. It was authored by Michael Murack, University of Ottawa; Rajini Chandrasegaram, Cardiff University; Kevin B. Smith, University of Ottawa; Emily G. Ah-Yen, University of Ottawa; Étienne Rheaume, University of Ottawa; Étienne Malette-Guyon, University of Ottawa; Zahra Nanji, University of Ottawa; Seana N. Semchishen, Simon Fraser University; Olivia Latus, University of Ottawa; Claude Messier, University of Ottawa; and Nafissa Ismail, University of Ottawa.