Children who have older fathers are more likely to have bipolar disorder according to a study  published in the U.S. journal Archives of General Psychiatry. Women on the other hand don’t face this risk since the number of eggs a woman carries is set at birth, each having divided 23 times at that point and no more. Australian psychiatrist Gordon Parker, executive director of the Black Dog Institute, said the findings were important, and might explain why diagnoses of bipolar disorder had been increasing.

Bipolar disorder is a form of mood disorder characterized by a variation of mood between phases of manic or hypo manic elation, hyperactivity and hyper imagination, and a depressive phase of inhibition, slowness to conceive ideas and move, and anxiety or sadness. Together these form what is commonly known as manic depression. Symptoms of mania and depression are present at the same time. The symptom picture frequently includes agitation, trouble sleeping, significant change in appetite, psychosis, and suicidal thinking. Depressed mood accompanies manic activation.

he Swedish researchers used a national medical registry to identify nearly 14,000 men and women diagnosed with bipolar disorder. For each person, they also randomly selected five people of the same sex and age without the condition. The researchers found that children born to fathers older than 30 had an 11 percent higher risk of developing bipolar disorder compared to younger fathers. Children whose fathers were older than 55 had a 37 percent increased risk. Scientists believe that as men age there is a greater risk for sperm mutations that could contribute to disorders in their children.