Sleep patterns can help predict which adolescents might be at greatest risk for developing depression, a researcher at UT Southwestern Medical Center has found in a five-year study.
Sleep is a biological factor known to be associated with adult depression. Depressed adults experience rapid-eye-movement (REM) sleep earlier in the sleep cycle than people who are not depressed. Until this study, available online and in the July edition of Neuropsychopharmacology, it had been unclear whether this relationship held true in adolescents.
Dr. Uma Rao, professor of psychiatry at UT Southwestern and lead author of the study, found that adolescents with a familial risk for depression but without a depression diagnosis experienced shorter REM latency, meaning they reached the REM stage more quickly. Those adolescents were more likely to develop depression by the end of the five-year study period than those who reached REM sleep later in the cycle.
"Sleep is probably more helpful in determining who is at risk for developing depression than in being a diagnostic marker for depression since REM latency of those adolescents was shorter before they even developed the illness," Dr. Rao said.
Adolescent depression is complex to prevent and to treat in part because baseline levels of sleep and other factors used to diagnosis depression are not clearly defined. For example, in clinical studies, adolescents without manifestation of mental illness can be labeled erroneously as control group members because they haven't yet reached the highest-risk period for developing depression � mid- to late-adolescence and early adulthood.
"Comparing these younger adolescents to those already showing depression obscures study results and can affect our understanding of the underlying mechanisms for depression as well as its treatment," Dr. Rao said. "Long-term studies may be helpful in determining which research participants should be considered as part of the control group. This study is an initial step in determining baseline measures that differentiate healthy adolescents from those who are likely to develop depression, bipolar disorder and other mental diseases as they get older."