Effect of fluoxetine on melatonin in patients with seasonal affective disorder and matched controls

BACKGROUND

The aim was to investigate the secretion profile of melatonin and seasonal affective disorder before and after treatment with fluoxetine.

METHOD

A six-week case-controlled study with repeated overnight blood sampling was conducted. Ten patients fulfilling the criteria for major depressive disorder, seasonal type, with a 29-item Hamilton Depression Rating Scale (HDRS) score of at least 20 were compared with ten age- and sex-matched healthy controls in a clinical laboratory. The effects of fluoxetine (20 mg/day) on the HDRS and melatonin concentration were measured.

RESULTS

Fluoxetine significantly reduced melatonin levels in both groups. There was no significant difference in melatonin secretion between the groups.

CONCLUSIONS

The effect of fluoxetine differs from tricyclics and fluvoxamine, both of which increase melatonin.

The effect of temazepam on melatonin secretion and light sensitivity

Seven healthy male volunteers had their light sensitivity (melatonin suppression) and melatonin phase measured before and after treatment with temazepam (20 mg) for 7 days. Temazepam did not alter the circadian phase of melatonin secretion (the Dim Light Melatonin Onset, the timing of the peak of secretion), the total melatonin secretion nor the sensitivity of melatonin secretion to suppression by full spectrum light. This is an important negative finding which suggests that the short half-life benzodiazepine hypnotic temazepam does not confound tests of light sensitivity or melatonin phase.