Supporting the theory that parenthood offers a buffer against suicidal behavior, a new study finds that the more children a woman has, the lower her suicide risk.

There is a long-standing theory that the historically lower suicide rates seen among married versus unmarried women reflects a “protective effect” of motherhood, rather than advantages of marriage per se.

These latest findings give some support to that theory, researcher Dr. Chun-Yuh Yang, of Kaohsiung Medical University in Taiwan, told Reuters Health by email.

Looking at 30 years’ worth of data on 1.3 million Taiwanese mothers, Yang found that women with two children were 39 percent less likely than those with one child to commit suicide.

That risk was 60 percent lower among women with three or more children, Yang reports in the Canadian Medical Association Journal.

The findings are based on birth and mortality records for Taiwanese women who had their first child between 1978 and 1987. Yang followed death rates for the study group through 2007.

Suicide was uncommon regardless of the number of children the women had. Among women with one child, there were 11 suicides per 100,000 women per year; that rate was seven per 100,000 among women with two children, and just under six per 100,000 among mothers with three or more children.

When Yang factored in a number of other variables - including the women’s age at first birth, marital status and education level - the number of children a woman had remained linked to suicide risk.

It’s possible, Yang said, that women with a large brood of children benefit from greater emotional or material support when times are tough. Women who have several children also spend a larger share of their lives caring for young children compared with mothers who have one child; mothers who feel “needed,” Yang noted, may be less vulnerable to suicide.

However, the researcher said, it is also likely that women who are already more vulnerable to suicide - because of serious depression or other psychiatric illnesses - tend to have fewer children. This is probably an “important explanation” for the findings, according to Yang.

One previous study, Yang noted, found that women with no children showed a higher suicide risk than mothers in general. Again, that could signal some sort of protective effect of motherhood, or the fact that women with psychiatric disorders are less likely to have children.

Although the current study included only Taiwanese women, Yang said the findings are likely relevant to other countries as well. Studies done in Norway, Denmark and Finland have found a similar relationship between a woman’s number of children and her risk of suicide.

SOURCE: Canadian Medical Association Journal, online March 22, 2010.