Seasonal variations of human lumbar CSF neurotransmitter metabolite concentrations

While circadian rhythms of many biological processes have been well characterized in humans, variations throughout the year have been little studied. Lumbar cerebrospinal fluid (CSF) neurotransmitter metabolite levels for homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenyl glycol (MHPG) were determined in patients with schizophrenia and Alzheimer's disease. Samples from both groups taken during October through March had significantly higher levels of HVA and 5-HIAA, but not MHPG, than samples from April through September.