Light-stimulated release of melanopsin suppresses the nocturnal production of melatonin and is sending signals to multiple brain areas, including hypothalamic suprachiasmatic nuclei and thus controlling the release of the pineal hormone melatonin and therefore control the circadian rhythm. Consumption of sedatives and hypnotics was used as an indirect measure of seasonal variations in sleep disturbances among inpatients at University Psychiatric Hospital Vrapče.

Retrograde record analysis was performed from 1st January to 31st December 2012 on commonly used hypnotics and sedatives: zolpidem, nitrazepam, flurazepam, and midazolam.

The lowest consumption of hypnotics was recorded in the months of November, August and September while the highest consumption was recorded in January, December and March which can be seen in Fig. 1. Although there were differences in the monthly prescription of hypnotics, when it comes to seasonal patterns, there are no statistically significant differences.

There is no significant difference between the consumption of hypnotics in the observed seasons although the consumption of hypnotics is higher in the months with shorter daylight. This study attempted to correlate exposure to light and insomnia through the prescription of hypnotics and it is possible there are other important variables not included in this study.

The authors have not supplied their declaration of competing interest.