Mental health problems can have a devastating impact on people’s lives and cost the UK an estimated £77 billion per year. Dr Milton and colleagues aim to understand how and why such disorders occur, and to develop new treatments. They use rodent models to define the psychological, neurobiological and neurochemical bases of different mental health disorders, to investigate why certain subpopulations are more vulnerable than others, and why they respond differently to treatment.

The researchers use rats and mice because the brain circuitry implicated in many mental health disorders is highly conserved between rodents and humans, and the behavioural tasks that they have developed are widely recognised as modelling specific aspects of these disorders. Rats and mice are also the least sentient species that can model these complex neuropsychiatric disorders.

This research is only possible with the use of animals. Human studies (for example brain imaging studies) are useful, but can only provide correlative data that do not address the cause of the disorders. Furthermore, it is not ethically possible to study the genetic and/or environmental factors that underlie predisposition to, and the development of, mental illness in humans. Similarly, it would not be possible to develop new treatments for brain disorders without testing them in animal models first. In vitro models (such brain slice preparations) or computer simulations cannot be used because the modelling of behaviour in these systems is not sufficiently advanced. Instead, the researchers use the minimum number of animals possible to develop new forms of treatments for mental health problems that cause suffering and distress in humans.