One in 12 adults has taken "smart drugs" - with most trying them at work, a survey shows.

Neuroscientists said growing numbers of people were turning to medication in a bid to cope with workload pressures.

And they warned that the pills could cause long-term damage, with little research tracking the consequences over a lifetime.

"Smart drugs" are illegal to sell without a prescription in the UK, but not illegal to buy.

Among the most commonly used are Adrafinil and Modafinil, which are usually prescribed to patients with sleeping disorders, along with Adderall and Ritalin, which are both stimulants primarily used to treat ADHD.