Animal models: Trait or state measure? The test-retest reliability of the elevated plus-maze and behavioral despair

1. The use of animal models in certain types of psychobiological studies (f or instance, the relationship between anxiety and depression) requires that the behavior measured is stable over time. 2. The test-retest reliability of the elevated plus-maze indexes of anxiety and the immobility time in the behavioral despair were evaluated. 3. The behavior of two groups of drug naive mice was measured on two occasi ons on the same test, 1 week apart, on the elevated plus-maze or on the beh avioral despair and then the intraclass correlation coefficient and kappa w ere calculated. 4. These behaviors showed a very low intraclass correlation coefficient (0. 02 - 0.05) and low kappa (0.08 - 0.21) in the test-retest design, which sug gest a poor reliability of these measures. 5. These results suggest that the behavioral parameters of the elevated plu s-maze and the behavioral despair are not stable and therefore they are pos sibly more related to state than trait characteristics. Therefore they appe ar to be not appropriate to evaluate trait characteristics which are suppos ed to be stable over time without treatment.