Nearly 40 percent of Europeans suffer each year from a mental disorder and only one third of all cases receive treatment, a new study has found.

The three-year multi-methody study published Monday in European Neuropsychopharmacology covers 30 countries and a population of 514 million people. The study spans 30 countries and ages 2 and above.

The two main areas “we have to address” include closing an “immense treatment gap” for mental disorders jointly approach mental and neurological disorders, according to principal investigator Hans-Ulrich Wittchen.

The most frequent disorders include anxiety disorders at 14 percent, insomnia at 7 percent, major depression at 6.9 percent, somatoform disorders at 6.3 percent, alcohol and drug dependence at less than 4 percent, attention-0deficit and hyperactivity disorders at 5 percent in the young, and dementia at 1 percent at those aged 60-65, and 30 percent among those 85 and above.

There were no significant cultural or country variations found except for substance disorders and mental retardation, the study found.

The few people receiving treatment do so with “considerable delays” of an average of several years, the study says.

The four most disabling single conditions were depression, dementias, alcohol use and stroke, as measured by disability-adjusted life years.

Among the challenges to improved basic and clinical research on such disorders are fragmentation in research and practice, the stigma and marginalization associated with brain disorders, and a lack of awareness by the public of the full range of mental disorders and their societal burden.