Hello everyone, One fifth of the people with bipolar disorder find their symptoms increase and decrease with the seasons. According to experts, decline in energy level, mood and motivation occurs in November and the person returns to normal level in April. Seasonal influences like temperature and light often affect our mood if we are in depression. This seasonal disorder is called seasonal affective disorder (SAD), which is a type of bipolar disorder, and is treatable with light therapy. It is difficult to look at the extent to which bipolar patients experience normal season mood variation. If we become depressed during late fall and winter, we return to normal mood during spring and summer. In bipolar disorder, a seasonal pattern patient tends to have manic or hypomanic episodes during specific season of the year. Marvin.