Chronic Form of Depression Runs in Families

The odds are more than two to one that people whose close relatives developed chronic severe unipolar depression when they were young will have it, too, according to results of a multicenter analysis of more than 600 people and their families.

Results of the study, published in the September issue of the American Journal of Psychiatry, with Johns Hopkins psychiatrist James B. Potash, M.D., as senior author, show that siblings, parents or children of people diagnosed with chronic major depression before the age of 31 have a 2.52-to-1 chance of also having the disorder. Moreover, first-degree relatives of patients diagnosed with chronic major depression before the age of 13 have a 6.17-to-1 chance of having it. "This chronic form of major depression can be uniquely disabling because of its persistence. Our finding that this aspect of the illness runs in families suggests the value of searching for contributory genes," Potash says, although he cautions that the results also could point to environmental factors, such as loss of a parent at an early age or physical and sexual abuse.

In this study, Potash and his team looked at 638 men and women diagnosed with early-onset major depression and 2,176 of their first-degree family members. The subjects were drawn from the Genetics of Recurrent Early-onset Depression (GenRED) project, a multicenter study of patients enrolled between 1999 and 2003 by Hopkins and other researchers.

Analysis showed that the 226 people interviewed in GenRED who were diagnosed before the age of 31 with chronic major depression had 352 family members who also suffered from this form of disease (37.8%), whereas the remaining 412 had a total of 148 relatives with chronic depression (20.2%). A breakdown of these results showed that 58 people diagnosed before the age of 13 with chronic major depression had 44 family members who also had the disease (48.9%). The remaining 69 people diagnosed with major depression before age 13 had 17 relatives (15.9%) with chronic illness.

"We have known for a long time that major depression runs in families, but we are still working on determining whether certain subtypes of the illness do so more strongly than others," says Potash. Our large study allows us the numbers to examine these questions in subgroups."

Potash credits lead author Francis Mondimore, M.D., of the Department of Psychiatry at Hopkins, with observing that many of the study participants reported having been depressed "as long as [they] can remember." This led Mondimore to focus on chronic - or persistent - depression over time. An estimated 30 percent of those with major depressive disorder have symptoms most or all of the time, with only incomplete remissions, over many years, according to Potash.

Mondimore says a similar technique, examining a subtype of illness, was used to discover a familial relationship in breast cancer in women - a finding that paved the way to discovering a link between the BRCA1 gene and that disease.