What can animal studies really teach us about disordered sleep-wake cycles and depression?

Sleep-wake cycle abnormalities and mood disorders such as depression are closely related. Understanding this relationship could lead to new and necessary treatments or help us altogether prevent these conditions and their associated health issues. Conducting potentially harmful experiments in humans is unethical, and in either case would be logistically impossible, meaning we rely on research observing individuals in their natural environments, which has limitations. Animal studies do not have all the same restrictions and could offer different opportunities. Given that certain conditions are met, animal experiments can be acceptable from an ethical standpoint. Researchers can easily source healthy animals that have never taken part in any prior testing and tightly control their environment and control the conditions of the experiment. Scientists may also conduct invasive but informative tests such as analysing brain tissue, blood samples or conducting behavioural tests, or administering treatments to test their effects. Thus, animal experiments offer many opportunities which are simply beyond our reach in humans. However, there are many questions about the usefulness and even relevance of animal studies. Does using genetically related animals and tightly controlling experimental conditions benefit us, when we are aiming to understand and treat complex human beings? Or can a mouse experience depression at all, and would we be able to tell if it did? Human and animal studies both have clear advantages, but also their own specific drawbacks. If we acknowledge the advantages and limitations of each, we can consider them together and use each to our advantage.