The signal substance serotonin plays a significant role in brain functions. The level of serotonin in the brain has been shown to affect our emotions and moods. The serotonin level in the brain is important in protecting against depression. Modern medicines for depression, so-called SSRI medicines (selective serotonin resorption inhibitors), work by raising the level of serotonin in the brain. The protein TPH-2 (brain-specific tryptophan hydroxylase), which is important for the regulation of the serotonin level in the brain, has long been suspected of playing a key role in the development of depression and manic depression.
The study, which was recently completed and is being published in the prestigious journal Archives of General Psychiatry, is based on an examination of what forms of TPH-2 (at the DNA level) are found in healthy individuals compared with the forms found in individuals with recurrent depression and manic depression, respectively. The different forms of TPH-2 people inherit can result in differing levels of serotonin in the brain, thus providing varying degrees of protection against depression. This comparison made it possible to show that the TPH-2 forms differed between healthy and affected individuals, which means that TPH-2 is involved in the development of these conditions. Certain forms were more common in healthy individuals, indicating that they have a protective effect against these conditions. There are as yet no clinical trials that have studied different THP-2 forms. All subjects who participated in the study live in northern Sweden.
The discovery of this hereditary protective factor, which is one of many, is a major piece of the puzzle in our understanding of the genesis and treatment of these disorders. Further research and economic resources are required for the discovery to lead to enhanced treatment and help for those affected.
The research has been carried out in a collaborative effort between a Swedish team of scientists under the direction of Professor Rolf Adolfsson and post-doctoral fellow Karl-Fredrik Norrback at the Research Unit of the Psychiatric Clinic in Umeå and the Department of Clinical Science, Section for Psychiatry, at Umeå University and a Belgian team of researchers from Antwerp University led by Professor Jurgen Del Favero and Ann van Den Boogaert, PhD. The study is being published in the prestigious journal Archives of General Psychiatry (Brain-specific tryptophan hydroxylase, TPH2, is associated with unipolar and bipolar disorder in a northern Swedish isolated population, 2006).
Depression is one of the most common disorders in the Western world, and according to the WHO (world Health Organization) it will be the most frequent disease by 2020. Three of ten Swedes experience depression some time during their lives, but it is still largely not known why. It is estimated that some 10 percent suffer from recurrent depression and an equally large group experience mood swings with varying degrees of manic depressive disease. Despite the fact that these disorders cause a great deal of suffering, increased risk of suicide, and shortened lifetimes, as well as major socio-economic costs for society, the causes of these diseases are still largely a mystery. However, scientists agree that the conditions develop through a combination of heredity and environment, such as stress. Far too few research resources are still being allocated to scientists wishing to study mental health, even though the attitude toward research on mental health is improving.