Antipsychotic drugs are generally used to control psychotic symptoms in patients with disorders such as schizophrenia, and some severe forms of depression.

Previous research suggested only some types of the drug increased the risk, particularly for people with dementia.

However a study published in the British Medical Journal says all forms of antipsychotics boost the risk, in all patients.

A mental health charity said patients on the drugs must be closely monitored.

Antipsychotic drugs fall into two types - newer "atypical" and older "typical" antipsychotics.

When the first concerns were raised in 2002, these focused on the "atypical" drugs.

Atypical antipsychotics are second-generation medicines designed to cause fewer neurological complications than conventional antipsychotics. They include aripiprazole (sold as Abilify), olanzapine (Zyprexa), quetiapine (Seroquel), risperidone (Risperdal), and ziprasidone (Geodon). Each is approved by the Food and Drug Administration to treat schizophrenia and bipolar disorder, and risperidone is also approved to treat irritability in children ages 5 to 16 who have autism.

The worries relating to atypicals led to a recommendation from drug safety watchdogs in the UK that they not be given to people with dementia, and the government has been urged to strengthen this in England in its forthcoming dementia strategy.

The latest findings, from researchers at the London School of Hygiene and Tropical Medicine, confirm the fears over dementia patients, but raise wider concerns.