Xu J, et al. - Researchers determined the associations among smoking status, sleep quality, and cerebrospinal fluid (CSF) glutamate levels in non-smokers and heavy smokers. In these subjects, the concentration of CSF glutamate was measured by spectrophotometry, and subjective sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI). They observed that the heavy smokers group vs the non-smokers group had poorer subjective sleep quality and lower CSF glutamate concentrations. Additionally, they observed that CSF glutamate levels and PSQI scores were not correlated in the heavy smokers.