All patients must meet the diagnostic criteria for recurrent major depression or bipolar mood disorder. Seasonal affective disorder (SAD) is then a sub-type specifier used to describe temporal variations of these disorders. As such, SAD is not considered a stand-alone diagnosis or comorbid condition to recurrent major depression or bipolar disorder. Common presentations include the initiation or worsening of depressive symptoms during the autumn or winter months, and full remission during the spring or summer months, or hypo-manic or manic symptoms presenting during spring or summer months.
Circadian and neurotransmitter factors are likely to contribute to the pathophysiology of SAD, although the exact mechanism of action remains ill-understood. The suprachiasmatic nucleus (SCN) of the hypothalamus is being increasingly recognised as the 'master regulator' of several systems implicated in seasonal mood regulation. Diminished light during the autumn and winter may cause a phase shift in various circadian rhythms, including sleep-wake cycle, body temperature, hormone levels, and melatonin secretion.
Among the 207.571 deaths that occurred in singapore in 2008?2009, we focused here on the 69.571 deaths (33.5% of the total) that were non-infant premature deaths (1?74 yr); the remaining deaths were infant deaths (0.4% of all deaths), and deaths occurring in people aged 75 and over (66.1%). While the total number of deaths is similar in both sexes, the fraction of those deaths that occurs prematurely (as defined here before 75) is much higher in men than in women, representing 42% and 24% of the total deaths respectively.