Trinity College and St James' Hospital Dublin are involved in an international effort to identify the genes linked to clinical depression Dick Ahlstrom reports.
Researchers in the Republic and eight other international centres are two years into a concerted effort to identify connections between clinical depression and genetic make up. The study links psychological assessments with gene studies and ultimately could lead to new treatment opportunities for depression.
Earlier studies have suggested that certain mood disorders may have a genetic component, but this is "still disputed", says Dr Natasha Afzal of the Trinity Centre for Health Sciences at St James' Hospital and Trinity College's Department of Psychiatry.
Researchers from nine centres in the US, Germany, Switzerland, Britain and Ireland have joined forces to accumulate a large amount of data involving about 1,200 "families", each including two or more individuals, explains Afzal.
The three-year Depression Network Project still has a year to run and is funded by GlaxoSmithKline. The Irish contribution is headed by Prof Michael Gill, professor of psychiatry at Trinity College and St James' Hospital, and the research team includes Ms Angela Cocoman and Mr Patrick O'Connor. "It is a collaborative study and we are the Irish site," Afzal says. "We are hoping to get 1,200 families and our Irish site is supposed to get 120 families. The minimum family is two affected family members, but ideally we should get two affected and one unaffected family member."
Depression is an illness which affects a person's physical, emotional, social and psychological well-being, she explains. Between four and 12 per cent of the population in western countries will suffer from major depression in their lifetime, but the real difficulty is that many cases go undiagnosed and therefore untreated, she says.
"Depression is a very general name and a misused term," she says. "You can be sad and people will say you are depressed. It is really a cluster of symptoms."
It is more common in females, who experience a 20 per cent lifetime risk of depression compared to a 10 per cent risk for men. Importantly, while up to 70 per cent of cases respond to treatment, an estimated 60 to 65 per cent of cases are never diagnosed, she says.
Afzal is also concerned about the "stigma" often attached to the disease. "People feel ashamed and won't come forward for treatment. Parents feel guilty they have passed it on to children." This is wrong, she says. People should come forward for treatment as with any other medical disorder.
Major depression is a persistent or recurrent depressed mood, characterised by feelings of sadness or emptiness. A confirmed diagnosis is based on the presence of at least five of these symptoms: a sad, low or empty mood; loss of interest or enjoyment in nearly all activities; feelings of worthlessness or guilt; difficulty in thinking, concentrating or making decisions; decreased energy, feeling fatigued or "slowed down"; changes in weight or appetite; oversleeping, early waking or insomnia; thoughts of death, attempts or plans of suicide.
While many people will from time to time experience one or more of these symptoms, a positive diagnosis is only made when these symptoms were present nearly every day for a period of at least two weeks, she says.
One of the keys to the study is deciding whether a person truly has clinical depression, and if so, what kind, she explains. The study is of depression only, the "unipolar" individuals with a mood disorder. The "bipolar" cases, those with both depression and mania, are not included in this research, Dr Afzal says.
"There are a lot of studies that have looked at bipolar and unipolar together. We are not studying those who have bipolar or schizophrenia," she says. "Our research is different from past studies."
All study members have agreed a standard set of criteria for entry to the study. "We are doing standardised questionnaires on personality. Once we know that the person fits for clinical depression, we take a blood sample for each individual."
The samples are "anonimised" so the individual's privacy is protected and samples are sent for analysis to a laboratory in St Louis, Missouri. "They are trying to identify genes or chromosomal regions that have the genes that make you more at risk for depression."
There is good evidence that there is a genetic link, she says. An identical twin has a 70 per cent risk of developing depression if the matching twin has it. A person has a 10 per cent increased risk of unipolar depression if a sibling has it and a 20 per cent increased risk if a sibling has bipolar disorder, says Afzal.
Even so, genetics is not the only answer. "You can't put it down only to environment or only to genetics. We do believe there is probably a couple of genes involved."
Identifying any genes responsible could be a great help in developing new drug therapies, she says. If genes are linked to the disease, then this opens the way to new drugs that can enhance or block the actions of these genes as a way to control symptoms.
Those willing to participate in the Irish part of the research programme can contact Dr Afzal at 01 473-3800, or by e-mail at Natasha@haughton-institute.ie