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Biomedical subjects

J L Karlsson

Publications and source records attributed to J L Karlsson.

At least 19 recordsLinked to original sources
PubMed2001

Mental abilities of male relatives of psychotic patients.

OBJECTIVE: Exploration of academic and creative potentials of first-degree relatives of hospital-treated psychotic patients in Iceland. METHOD: Relatives identified in a previously published family study of psychosis are evaluated, using records available at the National Archives and National Library in Reykjavik. Performance of groups of relatives is compared to that of the general population. RESULTS: Healthy relatives of patients are found to excel over others in authorship of books of fiction or poetry, in general school performance at age 20 years and in mathematics. These findings apply to both schizophrenia and affective illness. CONCLUSION: Relatives of psychotic patients often exhibit good mental abilities.

Creativity↗
PubMed1999

Relation of mathematical ability to psychosis in Iceland.

A study of mathematically gifted Icelanders demonstrates an increased risk of mental illness in their ranks. Psychotic disorders are also frequent among their relatives. Linkage of academic records with previously published data on the family distribution of psychosis reveals a pattern compatible with the hypothesis that high arousal plays a role in reasoning ability.

Achievement↗
PubMed1988

Partly dominant transmission of schizophrenia in Iceland.

Voluminous data on the familial distribution of schizophrenia in Iceland were evaluated in terms of a partly dominant genetic mechanism. The risks were found in most instances to be proportional to the probability of harbouring the proposed gene, but penetrance rates, which generally are around 25%, appear to be elevated when additional risk factors are present. This occurs in individuals with multiple ill relatives, in offspring of two schizophrenic people, or in monozygotic co-twins. Excessive risks also occur in families with unusually severe disease.

Genes, Dominant↗
PubMed1982

Family transmission of schizophrenia: a review and synthesis.

The more recent large scale family investigations of schizophrenia are reviewed, particularly studies in which the authors have compared the rates in relatives of index cases with those of the general population. The risk of psychotic illness is increased four-fold in first-degree relatives and two-and-a-half-fold in second-degree relatives over that of the population at large. The possible genetic mechanisms are evaluated, with the conclusion that modified dominant transmission, based on a single major gene, is a plausible system.

Adult↗
PubMed1976

Genetic factors in myopia.

A school population has been screened to locate same-sexed twins with myopia and also to compare intelligence test performance of myopic and nonmyopic individuals. Augmentation of the twin data by a survey of the world literature has led to the identification of a total of 106 MZ twin pairs, 100 of them concordant for myopia, as well as 41 DZ pairs, 12 concordant. Myopic students score eight points higher on IQ tests than nonmyopes, the entire bell shaped distribution curve being shifted to a higher range. The intellectual gain precedes in time the development of nearsightedness.

Adolescent↗
PubMed1975

Evidence of recessive inheritance of myopia.

Data are presented on the family distribution of nearsightedness, including the frequency of the disorder in the children of two myopes. The previous literature is reviewed, embracing several quantitative family or population studies in addition to extensive pedigree material. It is concluded that there is substantial evidence that recessive inheritance is the principal mechanism of transmission, and that most instances of myopia probably fall into that category.

Female↗
PubMed1975

Influence of the myopia gene on brain development.

Evaluation of the performance of 17-18-year-old high school students on standard intelligence tests confirms previous reports that nearsighted persons consistently achieve scores approximately eight I.O. points higher than non-myopes. Comparison of tests administered to the same students 10 years earlier suggests that the intellectual gain precedes the development of nearsightedness. Since there is convincing evidence from genetic studies that myopia is an inherited condition, probably transmitted as a recessive characteristic, it is concluded that the myopia gene has a stimulant action on the brain in addition to its effect on the eye. The high frequency of myopia in urbanized societies is explained in terms of an evolutionary adjustment, myopes probably having a survival advantage under conditions of industrialization.

Adolescent↗