Mania peaks in spring, and the risk varies by city
Moods follow the seasons. Rates of depression rise in winter and mania peaks in spring. It’s not the amount of sunlight that triggers spring mania but the rapid increase in light. That rate of change varies by region. The technical term for this rate is the “maximum monthly increase in solar insolation (kWh/m2/day).” I’ve calculated that figure using NASA data for major American cities so you can check your rate below.
In some cities, like those in the Northeastern U.S., there are two peaks in spring sunlight, but the peaks are relatively mild. The rise in sunlight is more intense in the Sunbelt and the Northern mid-west.
You can protect yourself from this rapid change in sunlight by wearing blue-light filtering glasses in the evening, starting about 2 weeks before the rate of change peaks in your area.
Rise in Spring Sunlight in U.S. Cities, from Most Rapid to Least Rapid
|City||Month of Rapid Increase||Rate of Change|
|Phoenix, AZ||April||1.59 kWh/m2/day|
|San Francisco, CA||April||1.53|
|Las Vegas, NV||April||1.52|
|Los Angeles, CA||April||1.49|
|Salt Lake City, UT||April||1.48|
|St. Louis, MO||April||1.45|
|Great Falls, MT||April||1.43|
|Sioux Falls, SD||April||1.34|
|Little Rock, AR||April||1.31|
|Kansas City, MO||April||1.30|
|Seattle, WA||March and April||1.19|
|Houston, TX||February and April||1.19|
|New York, NY||March and May||1.18|
|Detroit, MI||April and May||1.15|
|San Antonio, TX||February and April||1.13|
|Jackson, MS||April and May||1.13|
|New Orleans, LA||February and April||1.13|
|Atlanta, GA||February and April||1.12|
|Hartford, CT||March and May||1.07|
|Manchester, NH||March and May||1.01|
|Boston, MA||March and May||1.01|
|Montpelier, VT||February, March and May||0.96|
These figures were calculated from data at SolarInsolation.org and NASA. They reflect the total exposure of sunlight during the day and not just the length of the day. That means the angle of the sun is just as important as the duration of sunlight.
The relationship of spring sunlight to mania is derived from two lines of research. One has confirmed a rise in mania during the spring. The other has found that bipolar disorder starts earlier in people who grow up in places where there’s a dramatic rise in sunlight in the spring.