Seasonal affective disorder (SAD) is a form of depression that people experience at a particular time of year or during a particular season. Most of us are affected by the change in seasons it is normal to feel more cheerful and energetic when the sun is shining and the days are longer, or to find that you eat more or sleep longer in winter. However, the change in seasons will have a much greater effect on your mood and energy levels, and lead to symptoms of depression that have a significant impact on your day-to-day life.
patients with SAD become depressed in the winter, at least in part because of a phase delay in circadian rhythms relative to the sleep/wake cycle. The cause of this 'phase delay' and why it has such a pronounced effect on mood and behaviour, is likely to be multifactorial, involving abnormalities at various levels along the retino-hypothalamic tract, its links with the pineal gland, and the metabolism of melatonin and serotonin.
The fluoxetine group had lower depression scores at termination than the placebo group, but these differences did not achieve statistical significance. However, the rate of clinical response in the fluoxetine group (49%) was superior to that in the placebo group (68%). Post hoc analyses showed that the greatest fluoxetine responses were in the most markedly depressed patients and that overall response was greater for patients studied later in the season. Fluoxetine was well tolerated, and few subjects dropped out because of adverse events.