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Sleep and circadian rhythms, the 24-hour cycles of the body’s physiological processes, are important components of health. Likewise, disruptions in these systems are linked to a number of health conditions, including substance abuse. The developmental changes in sleep and circadian rhythms that occur during adolescence leave teenagers particularly vulnerable to addiction. 

A review recently published in the journal Biological Psychiatry by Pitt Department of Psychiatry researchers explored the link between sleep and circadian rhythm disruptions during adolescence and risk for substance abuse disorders. 

“A particular strength and novel aspect of our review is that it was authored by a multidisciplinary team of researchers from the Department who were able to bring together evidence from both animal and human studies,” said the article’s lead author, Ryan Logan, PhD, Assistant Professor of Psychiatry.

Adolescence is marked by several developmental changes in the circadian system. Circadian rhythms naturally become delayed, leading to later sleep and wake times; the drive to sleep that accumulates during periods of wakefulness takes longer to build; and sensitivity to the phase-shifting effects of light increases. At the same time, teenagers experience environmental changes such as greater exposure to light from electronic devices at night and earlier school start times, as well as social pressures to stay up later. This combination of developmental, environmental, and social factors result in inadequate sleep.

The review discusses a number of biological mechanisms by which disruptions to the sleep and circadian systems can influence the brain circuity responsible for reward processing and lead to vulnerability to substance use disorders. The authors propose a model in which a later timing and shorter duration of sleep, as well as the constant shifting between a forced early schedule during the school week and a later one on weekends, impair corticolimbic function in the brain. The result is an increase in reward seeking behaviors and a reduction in cognitive control that together increase the risk of addiction.

“The average teenager needs 8-10 hours of sleep per night, and most of them are not getting that. Our review highlights why sleep and circadian rhythms are particularly important for adolescents, and how disruptions during this critical time can have long-term consequences such as addiction,” explained the study’s senior author, Colleen McClung, PhD, Professor of Psychiatry and Associate Professor of Clinical and Translational Science. “The publication is very timely. Educators are beginning to pay attention to adolescent brain development and the fact that teenagers need adequate sleep, and are using this information to make decisions about school start times.” 

Although the review focused on the relationship between sleep, circadian rhythms, and substance use disorders in adolescence, these systems are also connected with risk for psychiatric disorders such as depression, anxiety, and attention deficit/hyperactivity disorder (ADHD). In a commentary accompanying the article, Ranier Spanagel, of the Central Institute of Mental Health in Mannheim, Germany, further explored the link between adolescent sleep and circadian rhythm disruptions and mood disorders.

The researchers conclude the review by suggesting a number of future studies. “We’re finally at a point in the research where we have to think about how to target and modulate the sleep and circadian systems, so we can then determine whether these interventions do something to reduce problematic substance use,” said co-author Brant Hasler, PhD, Assistant Professor of Psychiatry.

Impact of Sleep and Circadian Rhythms on Addiction Vulnerability in Adolescents 
Logan RW, Hasler BP, Forbes EE, Franzen PL, Torregrossa MM, Huang YH, Buysse DJ, Clark DB, McClung CA
Biological Psychiatry, 2018 83(12):987-996

Alterations of the Biological Clock May Contribute to the Emergence of Mental Disorders During Adolescence
Spanagel R
Biological Psychiatry, 2018 83(12):978-980