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.
age-adjusted three-year moving average amenable mortality rates from 1998 to 2009 for Israel. Amenable mortality rates have been decreasing steadily, for males by 31% from 110.0 per 100,000 persons in 1998–2000 to 76.3 in 2007–2009, and for females by 28%, from 93.3 to 67.9, respectively. This is a greater decrease than that for total mortality rates for the corresponding period, similarly age adjusted, which decreased by 25% for males and 24% for females for deaths under age 75.