Schizophrenia and Depression Co-Morbidity: What We have Learned from Animal Models

Abstract

Patients with schizophrenia are at an increased risk for the development of depression. Overlap in the symptoms and genetic risk factors between the two disorders suggests a common etiological mechanism may underlie the presentation of comorbid depression in schizophrenia. Understanding these shared mechanisms will be important in informing the development of new treatments. Rodent models are powerful tools for understanding gene function as it relates to behavior. Examining rodent models relevant to both schizophrenia and depression reveals a number of common mechanisms. Current models which demonstrate endophenotypes of both schizophrenia and depression are reviewed here, including models of CUB and SUSHI multiple domains 1, PDZ and LIM domain 5, glutamate Delta 1 receptor, diabetic db/db mice, neuropeptide Y, disrupted in schizophrenia 1, and its interacting partners, reelin, maternal immune activation, and social isolation. Neurotransmission, brain connectivity, the immune system, the environment, and metabolism emerge as potential common mechanisms linking these models and potentially explaining comorbid depression in schizophrenia.

Keywords: animal model; depression; genetics; mouse; schizophrenia.

Figure 1

Multiple shared pathways between rodent models which display both schizophrenia and depression-related phenotypes. This diagram illustrates the connections between each of the models (represented in color on the bottom right) and the biological processes which potentially underlie the observed phenotypes (represented in gray at the top left). Abbreviations: CSMD1, CUB and SUSHI multiple domains 1; DISC1, disrupted in schizophrenia 1; FEZ1, fasciculation and elongation protein zeta 1; GluD1, glutamate receptor delta 1; GSK-3α, glycogen synthase kinase 3α; MIA, maternal immune activation; NPY, neuropeptide Y; PDE4B, phosphodiesterase 4B; PDLIM5, PDZ and LIM domain 5; SRR, serine racemase; SI, social isolation.