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.
Although eating disorders have the highest mortality rate of any mental disorder, the mortality rates reported on those who suffer from eating disorders can vary considerably between studies and sources. Part of the reason why there is a large variance in the reported number of deaths caused by eating disorders is because those who suffer from an eating disorder may ultimately die of heart failure, organ failure, malnutrition or suicide. Often, the medical complications of death are reported instead of the eating disorder that compromised a person’s health. According to a study done by colleagues at the American Journal of Psychiatry (2009), crude mortality rates were: 4% for anorexia nervosa, 3.9% for bulimia nervosa, 5.2% for eating disorder not otherwise specified