So called reversed seasonal bipolar disorder is a pretty rare condition. My nephew developed it 6 years ago. No family history of mental disorders, but history of severe streptococcal infection during his childhood with the subsequent sepsis and Rheumatic fever. During his teenage years he stopped having any symptoms of Rheumatic fever, but at age 21 developed first episode of mania.It seems to be treatment resistant and only Zyprexa seems to control his symptoms to certain degree. Recently I found information how infection can cause mutation of the gene important in functioning of hypothalamus. Hypothalamus in turn is responsible for seasonal rhythm regulation, mood, regulation, hormones and immune system.
may I ask you if your son has relatives with mental condition. Has he had any serious health problems?