Bipolar disorder, a common psychological ailment, is significantly more common among individuals who were born by older fathers, according to a recent study. The study found that children born by fathers aged 29 or older were at increased risk for the condition.
Bipolar disorder encompasses a range of mood disorders that are characterized by episodes of mania, depression, or both. Mania is a state of extremely elevated moods, such as uncontrolled elation or hysteria. Sometimes individuals suffering from bipolar disorder suffer episodes, or cycles, of depression and mania, and some have mixed episodes of both. Lithium is a common medication treatment that stabilizes the episodes, but is not considered to be a cure for the condition. Causes for the disorder are greatly unknown.

Current researchers aimed to see if there was a connection between paternal age and bipolar disorder incidence. Past research had connected older paternal age to other neurodevelopmental disorders, such as autism and schizophrenia.

13,428 bipolar disorder patients, and five times as many controls, were analyzed in the study. The study authors found that "after controlling for parity [number of children], maternal age, socioeconomic status and family history of psychotic disorders, the offspring of men 55 years and older were 1.37 times more likely to be diagnosed as having bipolar disorder than the offspring of men aged 20 to 24 years. These were the extremes of paternal age, but it was seen that the offspring of a father 29 years or older was at an increased risk for bipolar disorder.

It was noted that maternal age had a similar, but much smaller, effect on the offspring. The authors explained, women are born with their full supply of eggs that have gone through only 23 replications, a number that does not change as they age. Therefore, DNA copy errors should not increase in number with maternal age. Consistent with this notion, we found smaller effects of increased maternal age on the risk of bipolar disorder in the offspring. The sperm of men on the other hand are known to change, or mutate, as they age, perhaps explaining why multiple neurological conditions, including bipolar disorder, are so closely linked to paternal age.