Iron deficiency is the world's single most common nutrient deficiency, and a well-known cause of impaired cognitive, language, and motor development. Many countries therefore routinely supplement infant foods with iron.

The study involved 1,292 children followed from birth, whose cortisol levels were assessed at 7, 15, and 24 months. Three tests related to executive functions were given at age 3.

In yet another study of the effects of pollution on growing brains, it has been found that children who grew up in Mexico City (known for its very high pollution levels) performed significantly worse on cognitive tests than those from Polotitlán, a city with a strong air quality rating.

Obesity has been linked to cognitive decline, but a new study involving 300 post-menopausal women has found that higher BMI was associated with higher cognitive scores.

In the last five years, three studies have linked lower neighborhood socioeconomic status to lower cognitive function in older adults. Neighborhood has also been linked to self-rated health, cardiovascular disease, and mortality.

Research into the effects of cannabis on cognition has produced inconsistent results. Much may depend on extent of usage, timing, and perhaps (this is speculation) genetic differences.

One survey of nearly 200 undergraduate college students who were not living with a parent or legal guardian found that 55% reported getting less than seven hours sleep. This is consistent with other surveys.

In the first mouse study, when young and old mice were conjoined, allowing blood to flow between the two, the young mice showed a decrease in