Associations Among Diurnal Salivary Cortisol Patterns, Medication Use, and Behavioral Phenotype Features in a Community Sample of Rett Syndrome.

Only 30 participants were analysed, and the sample was heterogeneous in age and medication use. There was no comparison group of females without Rett syndrome, so the study cannot show that cortisol patterns differ from healthy people. The study was exploratory, and p-values were not corrected for multiple comparisons, so the medication and behavior associations need replication. Only one participant showed the less-than-50% decrease on both days, so day-to-day variability was high. Samples were collected at home by parents, and only one morning sample was collected, so the cortisol awakening response was not accurately measured. Samples were sometimes collected only 8 to 10 hours after waking, which may have missed the normal evening low point. Medications were not randomly assigned, and the conditions being treated may explain the cortisol differences. Behavior and sleep questions were not validated for Rett syndrome, and clinical severity was not formally measured. Pubertal status was not collected, and older participants may represent a different population because of survival differences. Five samples had too little saliva and one sample had an implausibly high cortisol value, so not all collected samples were analysed.

The paper is tagged as supported by NIH extramural and non-U.S. government research funding. The supplied text does not report an author conflict-of-interest declaration.

Do not conclude that Rett syndrome causes abnormal cortisol patterns. The study had no comparison group, and only one participant showed the less-than-50% decrease on both days, so it cannot establish a stable group pattern.