The testosterone hypothesis: Assessment since Geschwind and Behan, 1982

Area of Science:

• Neuroscience
• Immunology
• Developmental Biology

Background:

• The Geschwind hypothesis suggests a link between non-right-handedness, immune disorders, and learning disabilities like dyslexia.
• This connection is theorized to be mediated by prenatal testosterone exposure.

Purpose of the Study:

• To review and evaluate the evidence supporting the Geschwind hypothesis.
• To explore potential neuropathological and immunological mechanisms underlying the proposed associations.

Main Methods:

• Review of epidemiological studies examining associations between handedness, immune disorders, and learning disabilities.
• Examination of neuropathological findings in human dyslexics and animal models.
• Discussion of potential immunological and genetic mechanisms.

Main Results:

• Epidemiological studies show mixed support for the Geschwind hypothesis; associations are stronger between learning disorders and non-right-handedness/immune disease than between the latter two.
• Neuropathological evidence is consistent with, but not diagnostic of, immunological pathology in dyslexia.
• Abnormal maternal-fetal interactions and genetic factors are proposed as potential underlying mechanisms.

Conclusions:

• Current data are not conclusive due to potential issues with sample representativeness.
• Immunological pathology and abnormal maternal-fetal interactions are plausible mechanisms for the Geschwind hypothesis.
• Further research is needed to definitively establish or refute the proposed causal links.