Today, depression is one of the most common mental illnesses, which can already begin in childhood and adolescence and can lead to severe psychosocial disturbance or even suicide. According to the figures of the World Health Organization WHO, more than 300 million people are suffering from a depression, which amounts to more than four percent of the world population. For Germany, the estimated number of people with depression in 2017 was at 4.1 million, which is 5.2 percent of the population. About 4.6 million people suffer from anxiety disorder. Despite many diagnostic methods, especially in children and adolescence, the disease is often only detected very late, which is why less than half of the affected children and adolescence receive appropriate treatment.
In children, depressions are quite rare, explains Prof. Dr. med. Gerd Schulte-Körne, director of the Clinic and Polyclinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy of LMU. “At elementary school age, between one and two percent are affected. In adolescence, it is much more common. And after puberty, the frequency then rises rapidly. Whether the disease is more common among children and adolescents today cannot be answered explicitly, on the basis of the data available. But the children and youth survey, a national survey in Germany, actually does show an increase among female adolescents between the ages of 16 and 18, however these look like mild forms of depression”.
The causes of depression are seen by scientists in genetics, neurobiological, social and psychological factors that can mutually reinforce each other. Although the disease can occur at any age – including adults – it often begins in childhood and adolescence, without being recognized. For a specific and effective treatment, it is however indispensable to know the risk factors that contribute to the development of the disease.
Many Factors as Triggers
“Certainly, many factors play a role, including individual pressure, as well as traumatic events. What we often experience is, that adolescents are today less capable of dealing with stress than in earlier times”, says Schulte-Körne. “In addition, the environmental impact on adolescents have changed significantly, in school and also in their leisure time, in the use of social media, for instance. And with the longer adolescence phase of today, the process of autonomy and separation from the parents’ home is also very different than it was ten years ago”.
An international team of researchers, led by the Max-Planck-Institute for Psychiatry in Munich and the Clinic and Polyclinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy of the Ludwig-Maximilians-University Munich, has thus genetically examined 2.000 children and adolescents with questionnaires and clinical interviews. Using the so-called genetic risk score, the scientists were for the first time able to predict, whether a child or adolescent has an increased genetic risk of depression.
“At the end, the score showed a comprehensive set of genetic information. It was a matter of variations in the genome, most of the time only tiny discrepancies, which when taken together, predict a specific characteristic or a disease, in this case a depression”, the scientist describes the way these scores function. “These genetic changes by themselves contribute only slightly, in total however, they form a score, which overall reflects the genetic risk of the person”.
Knowledge about the genetics of depression in adults already exists, researchers have now tested whether these genetic profiles are also suitable for predicting the origin, severity and onset of the illness in children and adolescents. ”This score was originally obtained from a very large sample of adults with a depressive illness and compared with a control group. The central question of our investigation was, if this genetic score is also relevant for children and adolescents and therefore suitable for determining the risk of disease in them as well”, says Schulte-Körne.
A Multi-facetted Disease
The results would have confirmed this. “In order to classify this progress, one has to say that depression has been studied for decades, until a genetic factor was found at all. The reason this was unsuccessful for a long period of time, is probably due to the fact, that depression is an illness with many faces, it is so multi-facetted, that genetic mechanisms only influence certain symptoms, but this does not explain the complexity of the disease as a whole.”
A large sample, comparing a group of children and adolescents with depression to a control group, showed that the score is also significant in children, says the youth psychiatrist. The researchers also investigated the relationship between the burden of depressive thoughts and emotions and this genetic score. “If a connection is to be found, this is first of all only a simple correlation. This is why in the next step, we try to find out whether there is a causality behind this”, Schulte-Körne continues.
“We also investigated whether in addition, stressful life experiences in early childhood (such as abuse) influence this relationship, and whether there is a connection between the genetic disposition and the severity of the disease or the age at which the illness occurs. If the latter is the case, and if the genetic score is relevant, this could mean that children with a higher risk for depression may get sick sooner.”
In the clinical sample, the research team found that the score explains eight percent of the depressive disorders in children and adolescents. “And when taking into account stressful environmental events or straining events in the life history, then you come to almost 18 percent of the depressive symptoms, which can be explained by it. And that is a relatively high value”, Schulte-Körne emphasizes. Essentially, it would first be about “developing a cause model of the depression and understanding, how genetic factors, individual pressures and environmental factors concur.”
With this study, an important step was made in understanding the complex genetic causes for depression in children and adolescents, says the researcher. However, the score only explains an increase of risk and not the disease itself. Therefore, there is still much to be done, in order to improve the early diagnosis of depression in adolescents, says the director of Max-Planck and director of the investigation, Elisabeth Binder. “If we however want to know, which children are more likely to develop a depression, we have the opportunity to use our preventive strategies, in order to reduce the tremendous burden of a depression.”