Depression as an evolutionary adaptation: implications for the development of preclinical models

Area of Science:

• Evolutionary biology
• Behavioral neuroscience
• Psychiatry

Background:

• Depression is often viewed as a disease state.
• Some researchers propose depression is an evolutionary adaptation linked to social structures.
• Adaptations arise from selection pressures, suggesting similar traits could evolve in various species.

Purpose of the Study:

• Identify social pressures that may drive the evolution of depression as an adaptation.
• Determine the potential benefits of depression as an adaptation.
• Evaluate if laboratory models (rats and mice) possess social organizations conducive to depression's evolution.

Main Methods:

• Conceptual analysis of social organization and evolutionary pressures.
• Review of existing literature on depression and animal behavior.
• Comparative analysis of social structures in wild rats and mice versus proposed adaptive scenarios.

Main Results:

• Depression may be adaptive in group-living animals competing for social rank and reproductive advantage.
• Depressive symptoms (altered activity, reduced sociability, increased submissiveness) can enhance survival after status loss.
• Wild mice and rats lack the specific social hierarchies and reproductive competition where depression would be advantageous, making them unlikely models for this adaptation.

Conclusions:

• Current depression models using rats and mice primarily study monoamine activity, not the proposed adaptive function of depression.
• Future research should utilize species with relevant social organizations to develop more accurate depression models.
• Understanding depression as an adaptation requires studying species with complex social hierarchies and reproductive competition.