The study involved 48 teens who were “at risk” for depression; they had a high risk because of a parental history of depression. The at-risk teens were compared with 48 other teens in a control group; these teens had no personal or family history of a mental health problem.
The research team monitored the sleep cycles of the teens for three days. They also used lab tests to measure levels of the hormone cortisol; increased cortisol levels are related to depression in adults. The teens were monitored for up to five years.
Results show that the at-risk teens took less time to enter the stage of rapid eye movement sleep – or REM sleep. They also had more REM sleep and elevated cortisol levels. These teens were more likely to develop depression by the end of the five-year study period.
Previous studies had shown that depressed adults enter REM sleep earlier in the sleep cycle; but it was unclear if this pattern also occurred in teens.
“This study is an initial step in determining baseline measures that differentiate healthy adolescents from those who are likely to develop depression,” lead author Dr. Uma Rao said in a UT Southwestern Medical Center statement.
Rao cautioned that REM sleep and cortisol levels are not diagnostic tools; but they are “vulnerability markers” for depression.
“If we can identify factors such as sleep and cortisol and their role, we could start the prevention process,” she said.
The NIMH reports that depression often occurs along with another disorder in teens; examples include anxiety, eating disorders and substance abuse. By age 15, girls are twice as likely as boys to have had a major depressive episode.
Earlier this year the Sleep Education Blog reported that sleep problems in children may predict the future onset of depression. A study showed that sleep problems at age 8 predict depression at age 10; but depression at age 8 did not predict sleep problems at age 10. The study found a strong genetic link for the presence of sleep problems.