Biopharmaceutical companies in the US currently have 187 new medicines in R&D for the treatment of mental illnesses, not including Alzheimer's disease, according to latest industry figures.

The new medicines - which are all now either in clinical trials or under review by the Food and Drug Administration (FDA) - include 52 for depression, 37 for schizophrenia and 26 each for anxiety disorders and addictive disorders, says the report, from the Pharmaceutical Research and Manufacturers of America (PhRMA).

Almost 60 million patients in the US suffer from some form of mental illness, but only a fraction of those impacted receive treatment, says PhRMA. And, according to the National Institute of Mental Health (NIMH), one in four American adults are affected by a diagnosable mental disorder, or 57.7 million in a year. Serious mental illnesses cost the nation more than $317 billion annually in lost wages, health care expenditures and disability benefits, it adds.

The treatments currently being developed by biopharma companies in the US also include 22 for sleep disorders, 20 for attention-deficit hyperactivity disorder (ADHD), 10 each for cognition disorders and developmental disorders, three for eating disorders and nine others.  Some of these medicines are in development for more than one condition, PhRMA points out.

Analysing the scale of the problem, the report says that an estimated 450 million people worldwide have some form of mental disorder. At any given time, around 10% of adults are experiencing a mental disorder and 25% will develop one at some point during their lifetimes.

Mental disorders account for 13% of the global burden of disease, and that figure will rise to nearly 15% by 2030, it adds, pointing out that depression alone is likely to be the second-highest contributor to the global burden of disease by that date.

Moreover, mental disorders are the leading cause of disability for people aged 15-44 in Canada and the US, and many suffer from more than one such condition at any given time, with 45% of those with any mental illness meeting criteria for two or more disorders.

Of the categories of disorder for which the largest number of new treatments are currently in development, depression affects nearly 21 million US adults, or about 9.5% of the population aged 18 and over in a given year.

Schizophrenia affects around 1% of the US population, while around 40 million adults - or 18% of people in that age group in a given year - are affected by anxiety disorders, it says.

Among the drugs currently in development by PhRMA member companies are: - a medicine to potentially treat the various symptoms associated with schizophrenia, with diminished side effects; - an intranasal medicine for anxiety which has been shown to improve symptoms within several minutes of administration; and - a potential first-in-class medicine for the treatment of major depression that recruits the patient's own neural stem cells to protect the central nervous system against damage from chronic exposure to stress.