Hibernation is an extreme example, but even species that do not hibernate often exhibit changes in behavior during the winter. The preponderance of women with SAD suggests that the response may also somehow regulate reproduction.Various proximate causes have been proposed. One possibility is that SAD is related to a lack of serotonin, and serotonin polymorphisms could play a role in SAD, although this has been disputed. Mice incapable of turning serotonin into N-acetylserotonin (by serotonin N-acetyltransferase) appear to express "depression-like" behavior, and antidepressants such as fluoxetine increase the amount of the enzyme serotonin N-acetyltransferase, resulting in an antidepressant-like effect. Another theory is that the cause may be related to melatonin, which is produced in dim light and darkness by the pineal gland, since there are direct connections, via the retinohypothalamic tract and the suprachiasmatic nucleus, between the retina and the pineal gland. Melatonin secretion is controlled by the endogenous circadian clock, but can also be suppressed by bright light.One study looked at whether some people could be predisposed to SAD based on personality traits. Correlations between certain personality traits, higher levels of neuroticism, agreeableness, openness, and an avoidance-oriented coping style, appeared to be common in those with SAD. Pathophysiology
Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-light therapy. SAD is measurably present at latitudes in the Arctic region, such as northern Finland (64°00′N), where the rate of SAD is 9.5%. Cloud cover may contribute to the negative effects of SAD.
Pyogenic granulomas appear on the gingiva in 75% of cases, more often in the maxillary than mandibular jaw. Anterior areas are more often affected than posterior areas. It can also be found on the lips, tongue, and inner cheek. Poor oral hygiene or trauma are usually precipitating factors.One study has suggested a correlation between pyogenic granulomas and Bartonella seropositivity. However, this association has been questioned by others. The microscopic appearance of a pyogenic granuloma consists of highly vascular granulation tissue. Inflammation is present. The lesion may have a fibrous character if it is older, and the surface may have ulcerations. Pyogenic granulomas rarely occur in the conjunctiva, cornea, or connective tissue of the eye following minor local trauma. Grossly, these mass lesions resemble those occurring at more common sites. The relationship of these lesions to lobular capillary hemangiomas of skin and oropharyngeal mucosa commonly referred to as pyogenic granuloma is uncertain. Associated conditions
Due to its overwhelming incidence on the gingiva, the condition is often associated with two other diseases, though not because they occur together. Instead, the three are associated with each other because they appear frequently on gingiva—peripheral giant cell granuloma and peripheral ossifying fibroma. Detailed analysis can be used to distinguish these conditions. Cause
Pyogenic granulomas are caused by proliferation of capillaries and are not caused by infection or cancer. Diagnosis
A doctor likely can diagnose a pyogenic granuloma based on its appearance, and might perform a biopsy to make a more accurate diagnosis.