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.
From 1991 to 2005, the death rate from coronary heart disease in Poland halved, resulting in 26 200 fewer coronary deaths in 2005 in people aged 25-74. About 37% (minimum estimate 13%, maximum estimate 77%) of this decrease was attributable to treatments, including treatments for heart failure (12%), initial treatments for acute coronary syndrome (9%), secondary prevention treatments after myocardial infarction or revascularisation (7%), chronic angina treatments (3%), and other treatments (6%). About 54% of the fall was attributed to changes in risk factors (minimum estimate 41%, maximum estimate 65%), mainly reductions in total cholesterol concentration (39%) and an increase in leisuretime physical activity (10%); however, these were partially offset by increases in body mass index (−4%) and prevalence of diabetes (−2%). Blood pressure fell in women, explaining about 29% of their decrease in mortality, but rose in men generating a negative influence (−8%). About 15% of the observed decrease in mortality was attributable to reduced smoking in men but was negligible in women.