How do people die with severe depression

Mental illness: if depression were cancer

This is what makes depression so vulnerable as a disease. "Even weirdos cannot deny the existence of pancreatic cancer and breast cancer," says psychiatrist and neuroscientist Eric Nestler of the Icahn School of Medicine at Mount Sinai in New York. "But somehow you can always say that people with mental illnesses aren't really sick. That's the really terrible thing about it."

Scientists are now looking for new ways to define and diagnose depression. In 2013, Thomas Insel, as head of the National Institute of Mental Health in Bethesda, Maryland, encouraged people to break new ground and avoid the classic psychiatric diagnoses, which are usually not clear and unambiguous. Instead, study patients should be grouped with the same specific symptoms, be it anxiety or social behavior problems, all of which are related to depression and other mental illnesses. With this focus, the researcher hopes, new diagnostic methods can perhaps be developed that eliminate disruptive factors and are based on biological principles. "Ultimately, every depression has just as much a biological background as cancer or heart disease. Here, the molecular basis only has to be deciphered," says Nestler. "That has turned out to be a lot more difficult than we all thought a few decades ago."

Hope genetics

Some scientists hope that genetics will help identify subsets of depression, as they have done with cancer. Many countries had invested huge sums of money here in recent years; the results have revolutionized the entire field of research, and there is now a long list of associated mutations that can be used to assign the most effective therapy possible to individual cancer patients. Research on this will continue, but it has already made the disease a pioneer in so-called personalized medicine.

Studies on depression weren't that successful. The largest genome analysis to date on more than 16,000 patients with severe depressive episodes and 60,000 control persons has so far only revealed a single, as before unconfirmed, genetic association. The psychiatrist Flint of the University of Oxford in England has been studying the genetic causes of depression for almost 20 years. Some colleagues have already asked him why he is still working on it, explains Flint. "The whole research area is not progressing because everyone always sees only unsolvable problems. And why should one work on something that seems unsuccessful to one?"

Once again, part of the problem is the imprecise definition of the disorder. Putting all patients who have had a major depressive episode in one group and looking for genetic factors would be like looking for genetic risk factors for fever, says Flint. "That would lump autoimmune diseases, infections, cancer and all sorts of other ailments into one pot." He also wonders whether more funding a few decades ago would have really advanced the field. After all, the technical basis for important investigations has only existed for about ten years. But even since then, cancer research has always been a few steps ahead. "Of course we can do better," says Flint. "We have to do better!"

The search for the genetic causes of other mental illnesses, such as schizophrenia, already looks more promising. Here, too, the exact diagnosis is often difficult and initial investigations into genetic risk factors provided only little information. The international Psychiatric Genomics Consortium has therefore set itself the goal of significantly increasing the number of cases in the studies in order to improve their informative value and not only work in the gray area of ​​statistics. In September 2014, the scientists published an analysis that was based on data from almost 40,000 schizophrenia patients and was able to link 108 different genetic regions to the disease. The researchers now want to try the same thing with depression, with a target sample size of 60,000 patients.