The possible link was uncovered in an analysis of mould and health conditions in several cities in eastern and western Europe. And it could one day lead to the addition of emotional problems to the list of health woes caused by mould, the study authors said.
But, the researchers cautioned, it's still too soon to tell if exposure to mould is directly related to depression, or whether an already depressed person might simply relinquish control of their surroundings to the degree that mould may develop.
"There is some preliminary evidence which suggests that high levels of exposure to mould may lead to depression," said study lead author Edmond D. Shenassa, an assistant professor of community health at Brown University School of Medicine.
"But it's not a certainty," he stressed. "We have found an association between mould and risk of depression, but we have more work to do to see if this is causal situation."
The study results are published in the October issue of the American Journal of Public Health.
How mould develops
Moulds are ubiquitous and toxic microscopic organisms called fungi that come in a variety of species numbering in the tens - or even hundreds - of thousands.
Mould spores, spread through air, water or insects, are found year-round both indoors and out, and survive and multiply most readily in warm, damp, shady and humid conditions, according to the US Centres for Disease Control and Prevention.
Typically, routine cleaning with soap, water and bleach can prevent mould from accumulating in the most susceptible areas, such as the seal of a refrigerator door, showers, windows and air conditioners.
But, a serious mould problem, easily evidenced by either the smell of a musty odour or the sighting of slimy, furry and discoloured patches on walls or ceilings, can develop and fester after excessive and continuous water damage.
The US government has not established general guidelines for acceptable levels of residential mould. And no study has conclusively linked mould exposure to mental health problems.
Mould is real health hazard
However, the CDC cautions that inhaling living or even dead mould spores can provoke an allergic respiratory reaction among sensitive individuals. Wheezing, shortness of breath and even lung infections can ensue, as can the onset of a stuffy nose, cough and headaches, and skin, throat or eye irritations.
Those most at risk include men and women suffering from allergies, asthma or the immune suppression that accompanies HIV infection, chemotherapy treatment for cancer and organ transplants.
To explore the possible link between mould and mental health problems, Shenassa and his colleagues reviewed World Health Organization data collected between 2002 and 2003 in eight European cities: Angers, France; Bonn, Germany; Bratislava, Slovakia; Budapest, Hungary; Ferreira do Alentejo, Portugal; Forli, Italy; Geneva, Switzerland; and Vilnius, Lithuania.
Almost 6 000 men and women in almost 3 000 households were questioned in person about their health, including whether they had been clinically diagnosed as depressed in the prior 12 months.
The participants, who ranged in age from 18 to 104, were divided equally between men and women and were chosen by random.
Living conditions a contributing factor
They were asked if they had experienced any of four symptoms of depression in the previous two weeks, such as problems sleeping, low self-esteem, poor appetite and/or a decreased interest in activities. Those with three or more symptoms were deemed to be depressed.
Residents were also asked to assess their living conditions, while, at the same time, the researchers conducted visual inspections to calculate the levels and location of any dampness and mould in each home.
Finally, each study participant was asked whether or not they felt in control of their home environment, as well as whether they had any of six conditions that can be associated with exposure to mould, including: cold or throat problems, wheezing, asthmatic attacks or other respiratory problems, fatigue or headaches.
Housing characteristics - such as light, ventilation, size, crowding and heating conditions - were also noted, as were basic demographic information such as employment status.
The researchers pointed out that such factors, as well as general health, are sometimes associated with depression.
Women and the elderly most at risk
Shenassa and his colleagues found that 57 percent of all the residents lived in homes that were free of dampness or mould, although the prevalence of mould varied greatly depending on region, ranging from more than 80 percent in Portugal to a little more than 25 percent in Slovakia.
Meanwhile, nine percent of all residents were determined to be depressed. Women, the elderly and the unemployed were most likely to have depressive symptoms, while those living in crowded conditions also appeared to run a higher risk for depression.
But, even after accounting for such key mitigating factors, the researchers connected the dots and found that having mould in the home appeared to be associated with depression.
"Basically, the risk for depression went up about 40 percent among people who lived in mouldy homes," said Shenassa.
"But although we saw there is more depression among people who live in mouldy homes, we don't know which came first," Shenassa cautioned. "We think there are multiple pathways to depression. So, we need to do more work."
lly A. Reynolds, a research microbiologist with the University of Arizona, described the study as "very interesting" but agreed further research is needed.
"Knowing that the mould health effects are long-term and chronic and sometimes cumulative means they [the study authors] might be very far from determining which is the chicken and the egg," she said.
"So, although there's a lot of speculation, it's difficult to prove a mental health connection. But what we always tell people is that if you can smell or see mould in your house, there's really no reason to not get rid of it."- (Alan Mozes, HealthDay)