Analysis of seasonal fluctuations of CSF monoamine metabolites and neuropeptides in normal controls: findings with 5HIAA and HVA.

Seasonal variations of certain cerebrospinal fluid (CSF) parameters have been reported in several psychiatric patient groups, but there is little or no available information on such variations in normal individuals. To evaluate possible circannual variations in the major CSF monoamine metabolites and an array of neuropeptide measures, we analyzed data from 20 to 34 normal volunteers studied over a 3-year period. Data were analyzed for seasonal and cross-seasonal fluctuations by one-way analysis of variance (ANOVA) followed by Bonferroni t tests when appropriate. The only statistically significant findings by ANOVA were for CSF 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA), both of which were lowest during spring and highest during summer. These spring-summer differences were statistically significant following Bonferroni t tests. These data support a growing body of evidence indicating a substantial seasonal effect on the serotonin system and suggest that any group analysis of CSF 5HIAA, and perhaps HVA, should take into account circannual variability.