Learning a second language may slow age-related cognitive decline, suggests a recent Scottish study in the Annals of Neurology, regardless of whether it was learned before age 18 or in adulthood.
The strongest effects were seen in reading, verbal fluency, and general intelligence. Knowing three or more languages was associated with even greater benefits.
The researchers controlled for factors such as baseline intelligence, sex, socioeconomic status, and immigration history. But it’s not possible to completely rule out “reverse causation”—that is, it may simply be that people with better cognitive function are more likely to become bilingual.