Drugs approved to treat attention deficit hyperactivity disorder (ADHD) pose certain health risks, and US Food and Drug Administration (FDA) instructed drug makers to put additional health warnings on the drug labels.

The drugs mentioned in the warning include Adderall, Concerta, Daytrana, Dexedrine, Focalin, Metadate, Methylin, Ritalin, and Strattera.

The risks include adverse cardiovascular and psychiatric symptoms. A small number of patients with underlying serious heart conditions on normal doses of ADHD drugs have suffered strokes and heart attacks, in some cases fatal, FDA reports. The adverse psychiatric events include hearing voices, becoming manic, or becoming suspicious for no reason. These events have even happened to people with no history of psychiatric conditions.

All the potential risks would be listed in The Patient Medication Guide. This guide should be read fully before the ADHD medication is taken.

"Medicines approved for the treatment of ADHD have real benefits for many patients but they may have serious risks as well," said Dr. Steven Galson, director of the Center for Drug Evaluation and Research (CDER).

"FDA is working closely with manufacturers of all ADHD medicines to include important information in the product labeling and in developing new Patient Medication Guides to better inform doctors and patients about these concerns," he added.

Among those who received the warnings are Eli Lilly and Co, Novartis AG, Johnson & Johnson, and Shire plc.

ADHD affects around 3 to 7 per cent of schoolchildren and 4 per cent of adults. The main symptoms are hyperactive behaviour, difficulty paying attention, and low impulse control.

Children and adults with ADHD tend to have low self-esteem, problems at school and work, and difficult relationships with family and peers.