In a pioneering study of 680 female homozygous and heterozygous twins, Kendler and associates found that the strongest predictors of liability to major depression were, in descending order: (1) stressful life events, (2) genetic factors, (3) previous history of major depression and (4) neuroticism. The authors concluded that major depression is a multifactorial disorder, and understanding its etiology will require the rigorous interaction of genetic, temperamental and environmental risk factors.
The many unresolved issues in behavioral genetics relates mainly to the fact that research methodology has lagged behind boldly expressed hypotheses"only by learning to use integrated, multifactorial etiological research designs will we get closer to unraveling the many causal pathways to affective disorders"(Cytryn and McKnew)
Not until the pioneering discovery of the limbic lobe by Paul Broca in 1878 was the centrality of the brain in human behavior gradually recognized and accepted. Aristotle, widely regarded as the father of Western biology, believed that the heart is the center of sense and feeling while the brain only cools and moderates the heart.
The recent emergence of the novel science of brain imaging permits a detailed visualization of brain structures and their function in vivo. The field can be divided into three major areas: (1) the structural examination of the brain, (2) the evaluation of brain function and (3) visualization of molecular brain structures such as receptors and neurotransmitters.
This beginning of our "window into the brain" started with the invention of computerized axial tomography (CT scan) in 1973. This was followed in the 1980s by the introduction of magnetic resonance imaging (MRI), which offers several advantages over CT, namely, no ionizing radiation and better quality imaging without the use of contrast injections. Brain activity is being investigated chiefly by positron emission tomography (PET) and single photon emission tomography (SPECT), both of which measure cerebral blood flow as an index of brain activity.
PET scanning also enables us to visualize neuroreceptors in vivo in the human brain. The distribution and number of specific receptors in the CNS, concentration of neurotransmitters at the synapse and the affinity of a receptor for a specific drug represent some promising areas of research which will greatly enhance our knowledge of brain neurochemistry in healthy and mentally disordered people.Vision of the Future
In the psychiatric office of the future, the patient with an affective disorder is likely to be referred to a radiologist to determine his or her structural and functional brain characteristics, including the localization of brain activity, the status of neuroreceptors, neuronal cell structure and neurotransmitter distribution. Genetic testing of the patient and his close family members will follow.
Such neurobiological analysis will help pinpoint the exact nature of the presenting disorder and facilitate a targeted, precise choice of therapeutic intervention, be it pharmacological or psychotherapeutic.
Recent biological advances lead many to believe that the future of psychiatry depends solely on neuroscientific progress. Such views are shortsighted and fail to encompass the complexity of human behavior. Rather, the mental health clinic of the future will also offer a choice of proven psychotherapeutic modalities, social skills training, crisis intervention, divorce and grief counseling, parent and teacher effectiveness training, and other modalities aimed at strengthening the emotional resilience of patient and family. Such a comprehensive biopsychosocial approach will ensure the necessary remedicalization of psychiatry, while preventing its dehumanization.