Not only is the human brain anatomically and functionally complex, but also a wide array of factors must be taken into consideration when designing and interpreting the results of studies of the human brain. Humans are genetically diverse with each individual having a unique exposure pattern to disease risk factors, including alcohol, tobacco, malnutrition, stress, and co-morbidities that may directly or indirectly affect the brain. Complex disorders such as alcoholism and schizophrenia that result from both intrinsic and extrinsic influences pose a range of scientific questions that need to be addressed by a combination of clinical, social, pathophysiological, and genetic approaches. While animal and other experimental systems may be able to model some of these factors, they are not able to fully reproduce the human condition. However, the convergence of animal and human study data can provide important insights in the understanding of the behavioral and mechanistic measures and molecular deficits relating to both addiction and mental illness.
