Schizophrenia causes hallucinations and memory or cognition problems in those who have it. This psychiatric illness affects 0.5% of the general population, and it can be related to genetic abnormalities of chromosome 22, known as 22q11 deletion syndrome. However, not everyone who has this deletion syndrome necessarily develops psychotic symptoms. So, what triggers the illness? Researchers at the University of Geneva (UNIGE), Switzerland, have provided an initial answer after observing and analyzing several years of patients with deletion syndrome. The scientists found that the size of the hippocampus (image), the area of the brain responsible for memory and emotions, was smaller than normal but followed the same developmental curve as in healthy subjects. Yet, when the first psychotic symptoms appear - generally in adolescence - the hippocampus atrophies dramatically. The new results, which were reported online on June 4, 2019 in Molecular Psychiatry, open up new avenues for understanding the causes of schizophrenia. The article is titled “Positive Psychotic Symptoms Are Associated with Divergent Developmental Trajectories of Hippocampal Volume During Late Adolescence in Patients With 22q11ds.” 22q11 deletion syndrome is a neurogenetic disorder that targets chromosome 22. Thirty percent of people affected by the syndrome end up developing psychotic symptoms specific to schizophrenia, such as auditory hallucinations, memory problems, disorders affecting their perception of reality, and difficulties in social interactions characterized by strong paranoia.
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