Reacción a "Reactions: Research finds that children of people with mental disorders are at increased risk of developing these and other disorders"

The onset of a mental disorder must be considered from a biopsychosocial model, i.e. both genetic and environmental factors play an important role. These factors are more frequent in some families than in others. Therefore, if a person has a parent with a mental disorder, he or she is more likely to develop a mental disorder than the general population. Over the last decade, it has become clear that some of the genetic susceptibility to mental disorder is shared between different disorders. Similarly, some of the environmental factors are risk factors for different disorders. Therefore, the question arises as to whether a person with a parent with a particular mental disorder is also at increased risk for a different mental disorder. This question is of great clinical relevance, both in the identification of subgroups of people at high risk for a psychiatric disorder for targeted prevention and in genetic counselling. In this case, it allows the family member concerned to be informed about the probability of developing the disorder in the future, if preventive measures are not taken. 

In recent years, there has been a considerable increase in the number of studies that attempt to answer this question. This paper compiles and analyses together the evidence generated by these studies. There are a total of 457 publications, so synthesising this data in a single publication is the great value of the work. The study analyses combinations of 10 different disorders to calculate risk estimates, which represents a useful tool in genetic counselling in families affected by a mental disorder. However, for many combinations of disorders, the amount of data available is very limited, which prevents accurate estimates. 

The meta-analysis is methodologically rigorous, although it presents a peculiarity in the design, as they decide to combine two very different types of studies. Thus, one part of the studies is based on the selection of families on the basis of whether or not the parents have mental disorders and carry out an exhaustive diagnostic examination of the offspring. In these cases, the number of individuals analysed is low, limiting the value of the study. In addition, the selection of families is based on clinical cases, which may have particular characteristics. Alternatively, other studies are based on electronic medical records. In this case, hundreds of thousands of people can be analysed, although there is an underestimation of the diagnosis, as there will be people with the disorder who do not seek medical care. The authors decide to give equal weight to the two types of studies. Another weighting would lead to different results. 

In summary, the paper is an update on a clinically relevant topic, which involves a great effort to synthesise the large amount of existing information. However, rather than representing a novelty at the conceptual level, it confirms previous data indicating that children of parents with a mental disorder are at elevated risk for both that particular mental disorder and a different mental disorder. It also provides updated, but generally imprecise, risk estimates. The work is published in a highly respected journal, the official journal of the World Psychiatric Association. It will therefore have an impact on the perception of psychiatric diagnoses not as watertight entities but as entities without clear boundaries and sharing causality, with the clinical consequences that this implies.