Genetics of schizophrenia in the South African Xhosa.

Africa, the ancestral home of all modern humans, is the most informative continent for understanding the human genome and its contribution to complex disease. To better understand the genetics of schizophrenia, we studied the illness in the Xhosa population of South Africa, recruiting 909 cases and 917 age-, gender-, and residence-matched controls. Individuals with schizophrenia were significantly more likely than controls to harbor private, severely damaging mutations in genes that are critical to synaptic function, including neural circuitry mediated by the neurotransmitters glutamine, γ-aminobutyric acid, and dopamine. Schizophrenia is genetically highly heterogeneous, involving severe ultrarare mutations in genes that are critical to synaptic plasticity. The depth of genetic variation in Africa revealed this relationship with a moderate sample size and informed our understanding of the genetics of schizophrenia worldwide.

Dementia in intellectual disability: a review of diagnostic challenges.

The evaluation of dementia in individuals with intellectual disability (ID), which will guide subsequent intervention, care and management depends on the systematic review of a number of factors: (1) the individual historical context, obtained from multiple sources, (2) evaluation of the pre-existing cognitive, behavioural, psychiatric, medical and adaptive skill profile, (3) the constellation, and pattern of evolution, of presenting signs and symptoms, (4) results of focused investigations, and (5) refinement of the differential diagnosis. In patients with ID, standard clinical methods need to be supplemented by careful, longitudinal behavioural observations, and individually tailored assessment techniques. Co-morbidity, multiple biological, psychological and socioenvironmental factors, and complex interactions among events, are the reality for many ageing people with ID. Determining the various influences is often a formidable clinical task, but should be systematically carried out using medical, cognitive, behavioural, neuropsychiatric and psycho-social frameworks.

Search for secular trends in calvarial diameters, cranial base height, indices, and capacity in South African Negro crania.

Two hundred eighteen South African Negro male crania were arranged in 5-year birthdate cohorts from 1880-1884, 1890-1894, up to 1930-1934 inclusive and investigated for the presence of a secular trend in their dimensions. Maximum breadth, maximum length, basibregmatic height, cranial base height, and bi-auricular breadth (BAB) were measured, and cranial index (CI), cranial capacity (CC), and cranial base height index (CBHI) were determined. Cranial length exhibited a significant increase from 1890 to 1930. Cranial base height and CBHI exhibited statistically significant declines over the same period. The absence of secular trends in the other dimensions studied corresponds to previous analyses of the lengths of the femora and tibiae of the same sample. The secular trends in cranial length, cranial base height and its index, and the absence of trends in the other dimensions, are discussed in relation to an apparent decrease in the standard of living occurring in this population after 1900. It is unlikely that the absence of a positive secular trend denotes the attainment of a genetically determined ceiling to the physical size of the subjects represented by these skeletons. It is more likely that the environmental factors believed to produce a positive secular trend were absent in the years from which this sample was drawn and that signs of improvement in these factors, if any, would be so recent that evidence of their effect is not yet available from our cadaver-derived skeletons.