Extrapineal melatonin and exogenous serotonin in seasonal affective disorder

The influence of daylight exposure on platelet 5-HT levels in patients with major depression and schizophrenia

Platelet serotonin (5-HT) can be used as a limited, peripheral model for the central 5-HT synaptosomes. Altered platelet 5-HT concentrations have been associated with psychiatric disorders like depression and schizophrenia. The aim of the present study was to compare platelet 5-HT concentrations during long, medium and short period of natural daylight exposure in a large number of medication-free male and female schizophrenic and depressed patients and sex-matched healthy controls. Platelet 5-HT concentration was determined spectrofluorimetrically in 240 (97 female, 143 male) schizophrenic and 258 (153 female, 105 male) nonpsychotic, nonsuicidal depressed medication-free patients and 328 (149 women, 179 men) healthy subjects during periods with short (<12), long (>12) and medium (average 12) hours of the natural daylight. Platelet 5-HT concentration was significantly lower in women compared to men in all groups. Healthy male subjects had significantly higher (p=0.011) platelet 5-HT concentrations during long compared to medium period. There were no significant differences (p>0.05) in platelet 5-HT concentration between different periods in healthy women. The significant increase in platelet 5-HT values were found in female (p=0.01) and male (p=0.029) depressed patients during long compared to short period. There were no significant associations between platelet 5-HT concentrations and different periods in both male and female schizophrenic patients. The results indicate the sex-related differences in the serotonergic system. The alterations of platelet 5-HT concentrations, observed across period with different durations of daylight exposure, point to a direct or indirect effect of light on peripheral 5-HT system that could be related to different sensitivity of the pineal gland to light and/or melatonin influence on 5-HT metabolism.

Seasonal variations in internalizing, externalizing, and substance use disorders in youth

Seasonal variations were assessed in symptoms of internalizing (anxiety and mood), externalizing (attention-deficit/hyperactivity and oppositional defiant disorders), and substance use disorders in youth. This study is based on secondary data analysis of two NIMH-funded epidemiologic-services studies: (a) Alternative Service Use Patterns by Youth with Serious Emotional Disturbance (N=936, ages 9-17); and (b) Methods for the Epidemiology of Child and Adolescent Mental Disorders (N=1285, ages 9-17). Child psychiatric diagnoses were measured by the Diagnostic Interview Schedule for Children. Variables that indicate site of the interview and service system, as well as age, gender, and ethnicity, were used as covariates. Significant annual variations were found in symptom counts of overanxious disorder, obsessive-compulsive disorder, separation anxiety disorder, social phobia, and major depressive disorder, with the estimated nadir in August-October. There may be weak seasonal variations in attention-deficit/hyperactivity disorder with estimated nadir in August, oppositional defiant disorder with estimated nadir in August-September, and marijuana use with estimated zenith in August-September. Significant seasonality in alcohol, other substance use, agoraphobia, and panic disorder was not found. There may be an instrument-specific bias in estimated nadir. Real nadirs may be up to 3 months prior to the estimated nadirs specified above. Findings suggest that seasonality in symptoms should be considered when assessment instruments of childhood psychiatric disorders are developed, as well as when epidemiological and clinical data are collected and analyzed.