Mental disease molecular theory

The time has come to create a molecular theory of mental disease. Instead of putting patients into diagnostic pigeon holes, such as depression, Parkinson s disease, or schizophrenia, that are poorly defined, heterogeneous, and nonspecific, we can use molecular imaging to relate a patient s problems to regional brain chemistry. 

The basic premise of this book is that we can create a molecular theory of mental illness, analogous to the germ theory of disease. Molecular imaging makes it possible to search for patterns in the chemical processes in the brain that are related to violence and other forms of mental illness, involving hormones, neurotransmitters, neuroreceptors, reuptake sites, ions, peptides, and proteins. 

Two diseases that were defined half a century ago can illustrate a molecular theory of mental disease. The rate of accumulation of radioactive iodine by the thyroid could be measured by radiation detectors pointed at the neck. Patients, who had a disease subsequently called hyperthyroidism were found to have an increased accumulation of radioactive iodine, whereas radioiodine uptake was low in patients with hypothyroidism. Patients with hyperthyroidism were nervousness and anxious, and suffered from weight loss, whereas hypothyroid patients were lethargic and had impaired mental functions. These two diseases illustrate the fundamental principle that if one can measure a chemical process in some part of the body, there will be patients in which the chemical process is abnormally slow, and others in which it is abnormally fast (Fig. 19.1). 

Most theories about the origin of mood disorders refer to the subcellular or molecular level, mainly emphasizing an imbalance between different transmitter systems [17] as a possible cause for unipolar depression as well as bipolar disorders. No concrete concepts exist to explain how and in which way such molecular disturbances modify the neural dynamics and lead to an increased mental vulnerability with progressive occurrence of disease episodes. 

---