SEATTLE -- To everything there is a season -- even divorce, new research from University of Washington sociologists concludes.

Associate sociology professor Julie Brines and doctoral candidate Brian Serafini found what is believed to be the first quantitative evidence of a seasonal, biannual pattern of filings for divorce. The researchers analyzed filings in Washington state between 2001 and 2015 and found that they consistently peaked in March and August, the periods following winter and summer holidays.

Their research, which they will present at the 111th Annual Meeting of the American Sociological Association (ASA), suggests that divorce filings may be driven by a "domestic ritual" calendar governing family behavior.

Winter and summer holidays are culturally sacred times for families, Brines said, when filing for divorce is considered inappropriate, even taboo. And troubled couples may see the holidays as a time to mend relationships and start anew: We'll have a happy Christmas together as a family or take the kids for a nice camping trip, the thinking goes, and things will be better.

"People tend to face the holidays with rising expectations, despite what disappointments they might have had in years past," Brines said. "They represent periods in the year when there's the anticipation or the opportunity for a new beginning, a new start, something different, a transition into a new period of life. It's like an optimism cycle, in a sense.

"They're very symbolically charged moments in time for the culture."

But holidays are also emotionally charged and stressful for many couples and can expose fissures in a marriage. The consistent pattern in filings, the researchers believe, reflects the disillusionment unhappy spouses feel when the holidays don't live up to expectations. They may decide to file for divorce in August, following the family vacation and before the kids start school. But what explains the spike in March, several months after the winter holidays?

Couples need time to get finances in order, find an attorney or simply summon the courage to file for divorce, Brines suggests. Though the same considerations apply in summer, Brines thinks the start of the school year school may hasten the timing, at least for couples with children. Suicides also tend to peak in spring, and some experts have said the longer days and increased activity elevates mood enough to motivate people to act. Brines wonders if similar forces are at play with divorce filings.

Brines and Serafini weren't initially looking for a pattern in divorce filings when they set out to investigate the effects of the recession, such as rising unemployment rates and declining house values, on marital stability. Poring over divorce filings for counties throughout Washington, they began noticing variations from month to month and were startled to see a pattern emerge.

"It was very robust from year to year, and very robust across counties," Brines said.

The pattern persisted even after accounting for other seasonal factors such as unemployment and the housing market. The researchers reasoned that if the pattern was tied to family holidays, other court actions involving families -- such as guardianship rulings -- should show a similar pattern, while claims less related to family structure wouldn't. And they found exactly that: The timing of guardianship filings resembled that of divorce filings, but property claims, for example, did not.

The divorce filing pattern shifted somewhat during the recession, showing a peak earlier in the year and one in the fall, and more volatility overall. Given uncertainty about financial considerations like housing values and employment, Brines said, it's not surprising the pattern was disrupted. But the shift in the pattern during the recession is not statistically significant, she said.

Their research excluded two of Washington's 39 counties, Lincoln and Wahkiakum. The small, rural counties are among few nationwide that allow marriages to be ended by mail, without a court appearance. Since anyone in Washington can file for divorce in the two counties, the researchers thought they would skew the results -- specifically, they figured filings might peak more quickly after the holidays, given the simpler process. But they examined filings in Lincoln County, the only county to accept divorce by mail since 2001, and saw the same pattern, albeit more pronounced, as elsewhere in the state.

"That leads me to think that it takes some time emotionally for people to take this step," Brines said. "Filing for divorce, whether you do it by mail or appear in court, is a big step."

The researchers are now looking at whether the filing pattern they identified translates to other states. They examined data for four other states -- Ohio, Minnesota, Florida, and Arizona -- that have similar divorce laws as Washington but differ in demographics and economic conditions, particularly during the recession. Florida and Arizona were among states hit hardest by the real estate collapse, and Ohio had higher than average employment rates.

Despite those differences, Brines said, the pattern persisted.

"What I can tell you is that the seasonal pattern of divorce filings is more or less the same," she said.