Researchers at Toronto’s Baycrest Centre for Aging are reporting “that the lifelong use of two languages can help delay the onset of dementia by four years compared to people who are monolingual.”

For some time now, researchers have been convinced that being well-educated, having a high-status job, and engaging in mentally-stimulating leisure activities build up a “cognitive reserve,” a stash of brainpower that seems to push back dementia symptoms as we age.  Bilingualism can now be added to this list of things promoting mental health.

Using more than one language was once thought to be unhealthy.  In the 1920s American psychologists regarded bilingualism as a disease, common among immigrants, that led to high rates of poverty, crime, and mental retardation.  In their view, two languages took up more space in the brain than one, making less room for really important knowledge.

Now cognitive scientists are saying that bilingualism has some proven health benefits.  It stimulates blood flow to the brain, making it larger.  It increases attention span in young and old alike.  And according to the latest findings, using two languages staves off madness for 4.1 years.  (E. Bialystok et al.,“Bilingualism as a protection against the onset of symptoms of dementia,”  Neuropsychologia [Feb. 2007: 459-64].) 

While the results of the Toronto study are only preliminary, and your individual mileage may vary, they are extremely encouraging. Delaying the onset of age-related dementia could mean reducing dementia in a population by up to 47% (that’s because some of the bilinguals will die of other causes during the four years before they start showing symptoms of dementia).

Of course the study is not all good news.  The patients that the researchers looked at were already demented when they were studied.  But the researchers are reasonably sure that being bilingual won’t prevent or cure the pathologies that cause dementia, it just masks them temporarily.  And while bilinguals lose touch with reality later than their monolingual counterparts, once dementia does appear, it progresses just as rapidly in both groups. 

There’s also bad news in this research for immigration reformers.  Most of the subjects in the Toronto study were not Quebeckers fluent in French and English, as one might expect, but immigrants to Canada – a finding which suggests that immigration, instead of being a drain on a nation’s social services, may actually be beneficial for its mental health.

But don’t rush to dig under that border fence or load your iPod with foreign-language lessons, because the findings of the present study apply only to lifelong bilinguals.  For anyone reading this, if you’re not already bilingual, it’s probably too late.  Starting a new language now, or dusting off your high school French, like the other memory exercises that have become popular among seniors afraid they might be losing it,  might help you remember where you put the car keys, but they won’t keep you from forgetting what cars are for. 

But the Toronto study does raise an important concern for people who have only one language.  If bilingualism promotes mental health, then monolingualism might subvert it, and a public policy that pushes monolingualism may not be in the national interest.  Nonetheless, that’s exactly the policy that most Americans seem to favor.  Ten years ago, Californians passed a referendum banning bilingual education.  In 2002 Iowa, where almost everyone is a monolingual English speaker, made English its official language.  Last November, Arizona voters joined the official-English bandwagon.  Towns all over America are declaring English their official language.  And this month, an official-English bill was introduced in the Missouri state legislature.  If it passes, Missouri, which boasted a progressive, bilingual English-German school system in St. Louis in the 19th century, will join California, Iowa, Arizona, and 25 other states in the national plunge into English-only madness, reaffirming America’s status as the country where foreign languages go to die, and quite possibly adding early-onset dementia to smoking and obesity as threats to the nation’s public health.