Debunking the "Depression Gene"

Depression's causes continue to defy definitive answers.

In 2003, researchers reported to great excitement that they had identified what could be called a "depression gene" - a genetic link to the risk of major depression. But new analysis of the groundbreaking study now disputes this conclusion. The new analysis, conducted by researchers at the National Institute of Mental Health, finds no strong association between the gene and risk of depression, though it does affirm the study's findings on stressful life events as triggers for the illness.

The 2003 "depression gene" study was influential, as it benefited from advanced technologies emerging in genetic research and suggested possibilities for gene-based therapies. The study found that a gene involved in serotonin activity increased the risk of depression among individuals experiencing stressful life events over a five-year period. The study thus offered hope for genetic testing and treatment for depression.

However, the study's results have not been consistently replicated. Though the role of the presumed high-risk gene was not supported, researchers did find a correlation between stressful life events and depression risk. Moreover, the findings do not exclude the possibility of some other genetic influence on mental health.

"Rigorous reevaluation of published studies provide the checks and balances necessary for scientific process," notes NIMH director Thomas R. Insel. "We are still in the early days of understanding how genes and environment interact to increase the risk for depression."

Depression reportedly affects about 121 million people worldwide, according to the World Health Organization, and is among the leading causes of disability. And while researchers debate depression's causes, patients seek solutions. Antidepressant use among Americans nearly doubled in the decade between 1996 and 2005, with more than 10% of people over age 6 reportedly receiving antidepressant medications, reports NIMH.

In Spain, nearly one-fourth of women now take antidepressants and 30% take tranquilizers, according to a new study published by the journal Atención Primaria. Rather than studying the genetic risks for depression, however, the Spanish study focused on environmental factors, specifically problems within the family and stressful life events (SLEs). Again, their conclusions were not clear.

The researchers speculated that family dysfunction was a contributing factor to women's mental health problems, but found this not to be the case.

"The use of psychopharmaceuticals is often related to family or work-related problems. We wanted to see if there was actually a positive link between the consumption of antidepressants and benzodiazepines and any kind of family dysfunction," lead author Sonsoles Pérez, a doctor at the Las Águilas Health Centre in Madrid, told the Spanish science news service SINC.

The researchers used the Apgar test, a protocol for measuring family functionality (e.g., cooperation, adaptability, affection, social maturity), as well as records of stressful life events, or SLEs (e.g., births, deaths, divorces, job loss), which often trigger mental illnesses. They compared these measures with the survey subjects' prescribed use of antidepressants and benzodiazepines, which are often used for insomnia.

"Although one might think that family conflicts lead to greater consumption of psychopharmaceuticals among women, we did not find any such relationship," Pérez reports.

The researchers did find that use of benzodiazepines increased with age, but that use of antidepressants did not, suggesting directions for further research into understanding the relationship among family dysfunction, stressful events, and mental health, as well as what interventions or medications are most appropriate to treat individuals.

"We think that greater training is needed in identifying SLE and family dysfunction, and recording these in patients' records in order to help psychologists, psychiatrists, and primary health-care specialists," Pérez concludes.

Untangling the mysteries of the human mind is complicated by the many interacting risk factors, both genetic and environmental, and finding the exact combinations of risk factors that trigger depression continue to challenge researchers. Meanwhile, depression continues to afflict more individuals - and their families.

Sources: National Institute of Mental Health, National Institutes of Health, www.nimh.nih.gov.

Plataforma SINC, Fundación Española para la Ciencia y la Tecnología, www.plataformasinc.es.