Dr. Gow said previous research with the Lothian group suggested people who participated in more social and intellectual activities at age 70 and had better cognitive abilities were the ones who scored higher on mental ability tests at age 11.

WSJ: Exercise Might Beat Puzzles for Protecting the Aging Brain

In 1947, almost all 11-year-old children attending school in Scotland were given intelligence and mental-health tests.

WSJ: Exercise Might Beat Puzzles for Protecting the Aging Brain

The numeracy tests cover reading graphs and tables, as well as mental arithmetic questions including percentages and fractions.

BBC: Literacy and numeracy tests toughened for new teachers

They said he had been transferred to a different hospital after tests suggested he had reacted poorly to medication prescribed as part of his mental health treatment.

BBC: Shrien and Anni Dewani

Before beginning the study, participants were given standard cognitive tests, many involving executive-function tasks such as concentration and shifting from one mental task to another.

WSJ: When Computer Games May Keep the Brain Nimble

After 18 months, the average mental decline in the DHA and placebo groups was nearly identical, as measured on two separate tests and rating scales.

CNN: Fish oil ingredient doesn't slow Alzheimer's

Tait, who returned to action earlier this year after taking a break with mental and physical exhaustion in 2008, has played 22 one-day internationals as well as three Tests for Australia.

BBC: Glamorgan sign Australia fast bowler Shaun Tait

Further tests showed that DISC1 acts like lithium, a drug commonly prescribed as mood stabiliser to patients with mental illness, inhibiting the action of a key chemical in the brain.

BBC: Gene 'has key schizophrenia role'