At first glance, it seems to make sense that as definitions of a mental health problem change, so the research surrounding it should be corrected to meet the new definition. If not, then you can run into all kinds of difficulties. For example:

1. If you’re doing a treatment vs. control RCT into an antipsychotic, for instance, you risk having participants who don’t meet the new diagnostic criteria for schizophrenia.

2. Similarly, in studies comparing groups of people who have the diagnosis and who don’t, then you might find you have people in your one group should actually be in the other.

But there are some questions and considerations to take into account.