In the first half of the nineteenth century, the prevalent interpretation of mental disorders was that of unitary psychosis, which considered the various forms of disease as successive stages of a single fundamental disorder. At the end of the same century that approach, strongly influenced by the romantic psychological thought, was surpassed by the epidemiological observations of Kraepelin. Distinguishing manic depression from dementia praecox, Kraepelin introduced a psychiatry made of nosographic autonomous entities, similar to those of other major medical specialties. Nevertheless, the unitary concept of mental illness, though a minority, has continued to be operating within the psychiatric field. As a proof of this, we can consider the recent proposals to make the diagnosis dimensional rather than categorical. A support for the theory of unitary psychosis comes from the results of a big study published in 2013 in the journal 'The Lancet', which suggest the presence of genetic alterations common to major psychiatric disorders, such as autism, ADHD, bipolar disorder, depression, and schizophrenia. This unprecedented research was conducted by members of the Psychiatric Genomics Consortium (GPC) on over 33,000 patients and 27,000 healthy control subjects, all of European origin. The object of the study were single nucleotide polymorphisms, frequently called SNPs. A SNP is a variation of the genetic material found on a single nucleotide. SNPs with minor allele frequency equal to or greater than 1% each are approximately 100-300 base pairs along the entire genome. Below the 1% threshold it is customary to speak of mutation. In the study of GPC, SNPs exceeded the threshold in four loci of p21 and q24 regions of chromosomes 3 and 10. Mutations pertaining to two protein subunits of voltage-gated calcium channels of L-type membrane of neuronal cells. According to Jordan Smoller, director of the center for genetics psychiatry at Massachusetts General Hospital in Boston, "this analysis provides the first evidence that the genome-wide genetic risk factors are the same both for psychiatric disorders with onset in childhood and for those that occur in adulthood, groups which are currently treated as separate categories in clinical practice”. In addition to supporting the idea of a common basis for psychiatric disorders, findings of this study have other important implications for psychiatry in the future. They indicate the possibility of classifying disorders -or perhaps it would be appropriate say “diseases”- no longer on the basis of the description of the symptoms but on the basis of the underlying causes. These results suggest the ability to predict, through a simple genetic analysis, the individual's risk of getting sick, significantly improving the possibilities for prevention. They may also help to identify new molecular targets for the development of new classes of psychotropic drugs. However, it is necessary to remember that the genetic alterations lead to the onset of psychiatric disorders only partially. They also depend on other factors, both psychological and socio-environmental. At the present state of knowledge, the influence of the genetic causes varies from disorder to disorder, with a minimum of 30-40% for depression up to a maximum of 70-80% for bipolar disorder or autism. As at other times in the past, even today in light of the new acquisitions in the field of genetics, unitary concept of mental illness prevails but does not impose itself definitively. In his “General Psychopathology” published in 1959 Karl Jaspers wrote: "The ones expounded the theory of unitary psychosis: there is no morbid unity in psychopathology, but only a huge variety of mental alienations, which continuously and in every way pass into each other... Others teach that the main task of psychiatry is to find those natural morbid unities that in theory are separate from each other, in presenting specific and common symptoms, courses, causes and somatic features, between which there are no steps. Although the struggle between the two trends has been conducted with great mutual disdain, though each party was convinced of the utter failure of the other, the historical fact that this fight is over only apparently and never really, makes us suppose that in both parts there is something right and that, instead of fighting, they could complement each other".
REFERENCES
- Cross-Disorder Group of the Psychiatric Genomics Consortium, Smoller JW, Craddock N, Kendler K, Lee PH, Neale BM, et al. (2013) Identification of risk loci with shared effects on five major psychiatric disorders: a genome-wide analysis. Lancet, Apr 20; 381(9875):1371-9.
- Gullotta C (1989) Unicità psicotica e molteplicità del disturbo mentale. In P. Aite e A. Carotenuto (a cura di) Itinerari del pensiero junghiano, Milano, Cortina.
- Jaspers K (1959) Psicopatologia generale. Roma, Il Pensiero Scientifico.