Which research studystudies focusesfocus on the interaction between the environment and genetics in the development of psychological disorders?

"Psychopathology" is the name of the field that involves psychological disorders. When you're looking at interaction between genetic and environmental factors, you're looking at "The interactionist approach".

To every topic, there are several approaches, e.g. your genetic makeup is the only factor in developing psychological disorders (Biological approach), or conditioning is the only factor (Behavioural approach), etc (there more approaches).

So in full, you're looking for "The interactionist approach to psychopathology"