Bipolar disorder: People with bipolar disorder fluctuate between intense depression and mania, interspersed by periods of relative calm. The exact causes of bipolar disorder aren’t known, but it appears to run in families. About 1 in every 100 people develop bipolar disorder in their lifetime Older fathers are more likely to have children with bipolar disorder, research suggests. The risk goes up when men are older than 29 before they start their family, and is highest if they are over 55. Increasing paternal age has already been linked with schizophrenia and autism, but not bipolar disorder, formerly known as manic depression. The Swedish study, in Archives of Psychiatry, suggests the risk may, in part, be explained by ageing sperm. DNA errors Unlike women who are born with all their eggs, men make new sperm throughout their adult life. The process of making sperm involves copying DNA, and this is prone to error, particularly as men age, say the Karolinska Institute researchers. Lead researcher Emma Frans explained: ‘Women are born with their full supply of eggs. Therefore, DNA copy errors should not increase in number with maternal age.’ Consistent with this notion, […]