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.
The leading cause of injury deaths among men in the Northeast region was homicide, followed by road traffic accidents and drowning. The risk of dying from homicide was 30% higher in this region compared with the South region, based on observed VR data , but this increased to 90% after applying correction procedures. After increasing steadily from 1980 to 2002, a reduction in firearm-related homicide in Brazil occurred after gun control legislation was enacted in 2004. Homicide and road traffic accidents are a much greater cause of death among males than females. Although mortality rates from traffic accidents based on crude death registration data were higher in the South region versus the Northeast region (data not shown), the correction methods that were applied suggest that they were relatively similar. Alcohol, excess speed, and poor conservation of roads and highways, as well as a high number of motorcyclists, are important determinants of the high death rate from traffic accidents in Brazil .