Maladaptive aggression is a commonly observed trait in psychiatric disorders, especially in the paediatric conduct disorders of interest to this project, ADHD and CD. These two disorders are also the most frequent psychiatric disorders in childhood and adolescence, with over 5% and up to 10% of the population below the age of 18 years affected [14] [31]. This means that there are more than 5.4 million affected children and adolescents in the European Union [41], which is why costs of treatment and direct non-medical health care amount to over €6.2 billion per year for this group.

Importantly however, the disorders are linked to lifelong serious impairment in social and occupational functioning, as ADHD persists into adulthood in 65% of cases and both disorders are strong predictors of the development of antisocial and substance use disorders, which underscores their huge impact on society. Costs associated with the adult outcome of the ADHD and CD are at least 10 times higher than those for childhood disorders [41].

ADHD and CD thus place large personal and economic burdens on individuals and society including the family and schools. The numbers above, computed from studies of youth, do not account for the impact of aggression and criminality in adulthood that accompanies the disorders. Additional impact on our society is thus caused on the victims of this aggression and also on the executive and judiciary legal systems. Crime statistics from Eurostat indicate that in 2009 (the most recent assessment date available), 127 in every 100,000 individuals from the adult and juvenile European population had been imprisoned for a crime (eurostat crime statistics). More detailed statistics available from the US show that approximately 30% of imprisonments are due to violent crimes, such as homicide, robbery, kidnapping, rape and other sexual assaults (Bureau of Justice Statistics).

Strikingly, when systematically meta-analysing the frequency of psychiatric disorders in adolescent detainees, CD (46-53%) and ADHD (12-18%) are the most frequently observed diagnoses [26] [27]. In adult detainees, ADHD-frequencies might even be higher, with a German study reporting a 45% prevalence of ADHD in male prison inmates [28]. It can thus be assumed that persistence of CD and ADHD, under certain negative environmental conditions, opens up a detrimental developmental trajectory leading towards aggression, violence and crime. Appropriate counteractive measures should ideally be prophylactic in nature, i.e. provided early on after definite diagnoses of the disorders, in order to prevent the very first violent-aggressive act.

Current behavioural and pharmacological treatment options for ADHD and CD are however insufficiently effective in treating aggression and have no proven curative potential in this respect. Designing new, improved treatments requires a deeper understanding of the molecular, cellular and brain-circuit-based underpinnings of aggression than is currently available. Strategies to prevent (escalation of) aggression in those susceptible to it require better markers of susceptibility at the genetic, epigenetic and brain-level, which have not yet been forthcoming.

Hence, it rapidly becomes clear that aggression is not a uniform construct and cannot be expected to be prevented or treated in a one-size-fits-all manner. Highly interdisciplinary approaches are needed to make progress in reducing the burden of aggression on society.

In the longer term, these measures will reduce aggression impact on society and will reduce the economic burden caused by paediatric conduct disorders. To achieve these impacts, the most important steps to be taken by the Aggressotype consortium are the following

In addition to the primary areas of impact, we also expect additional spin-offs from our project.