**Abstract**

Among the diseases affecting the brain, special attention has been paid to psychiatric disorders (PDs) due to high prevalence and significant debilitating clinical features. Many difficulties need to be overcome to find good animal models for PDs, due to their multifactorial origins, high heterogeneity and symptoms, as for instance the hallucinations and delusions, which usually cannot be easily assessed employing ordinary experimental animal models. The use of animal models reproducing at least some specific traits that can be studied individually, known as endophenotypes, is often reported. However, since altered biological pathways are common to many of these disorders, each of these behaviors may also reflect different PDs. In this context, it is possible to perform several approaches, to elicit changes in the endophenotypes of interest, not only in vertebrate models like rodents, but also in invertebrate models which have important advantages due to high conservation of essential pathways, lower complexity, and shorter life cycle compared to mammals. Therefore, animal models are also helpful for elucidating the etiology underlying PDs, by allowing easier access to biological samples that are usually not accessible in clinical studies, as for instance, fresh brain samples, from embryos to adults.

**Keywords:** animal model, psychiatric disorders, neurodevelopment, biomarkers, CNS, endophenotypes
