As many as one person in four has some form of brain condition, but many cases go undetected because people do not seek medical help, according to the public health agency RIVM.

A new study found that 3.8 million people are registered with their family doctor with a brain disorder. Half have a psychological condition such as depression or anxiety, while 1.3 million suffer from chronic illnesses such as dementia or Parkinson’s disease.

Sleep disorders, which affect around half a million people, brain injuries and inherited problems such as learning difficulties are also classed as brain disorders in the study carried out on behalf of the Netherlands Brain Foundation (NBF).

Women are more likely to have a diagnosed brain disorder than men, with around 2.1 million cases in women. However, the RIVM said the actual figures are likely to be much higher because many people do not seek medical treatment.

The total cost of treating brain conditions is around €25 billion a year, which represents more than a quarter of all health spending in the Netherlands.

The NBF said it had commissioned the study to highlight the fact that many disorders are invisible. ‘The next step is to tackle the issue through research, but also by improving treatment for patients in the hope that it will drive the costs down,’ said neuroscientist Laura Rigter.