Women have historically been pressured to have children before moving too far into middle age. At first this pressure was backed merely by social expectations, but more recently it has been backed by the scientific evidence that older women raise the risk that their children will develop serious health problems. For instance, the risk of Down Syndrome increases more than ten-fold for a mother over 40 years of age.  Older men have enjoyed the image of wise and healthy fathers. In the new millennium, however, evidence has been building that aging men also raise the risk that their children will develop mental illnesses.

A study by Dr. Emma Frans, published in the September issue of The Archives of General Psychiatry, demonstrates that as the age of fathers rises, so does the risk of bipolar disorder. Dr. Frans used meticulous records kept by the Swedish government to find 13,428 children with bipolar disorder, along with the ages of their parents at their birth. The ages of the fathers were divided into five brackets of five, starting from age twenty and ending with 55 and over. After adjusting for socioeconomic status and family history, there remained a strong correlation between age and bipolar disorder.

Children born to fathers in the 55 and over bracket were 37% more likely than the youngest bracket to have bipolar disorder. This correlation increased with each successive bracket. The effect of older mothers was only statistically significant in the bracket 35-39, and even this was not as high a correlation as the one found for fathers.  This result, combined with earlier work by Dr. Finn Rasmussen demonstrating that older fathers lead to more cases of schizophrenia, suggests that doctors and parents should pay attention to the age of both fathers and mothers so that they receive the appropriate counseling and testing.