An “Abundance” Phenotype Hypothesis for Autism

Abstract

Autism spectrum disorder (ASD) is significantly increased in recent decades, all over the world. The enlargement of the disorder’s diagnostic criteria and the increased accessibility of diagnostic and treatment services, are not the only factors that could explain the phenomenon.  Literature review was made in order to formulate a possible explanation for autism epidemics today. So, different phenotypic characteristics of autism (such as macrocephaly, megalosomy, obesity), laboratory findings (such as increased BDNF, IGF-1, IGF-2, IGFBP-3, GHBP, testosterone and oxytocin), and some autism risk factors (such as maternal metabolic conditions, prenatal and postnatal nutritional supplements, infant milk formula and breastfeeding) are discussed from an ecological and evolutionary neuropathology aspect and it is proposed that autism is the result of increased activation of growth pathways, especially at neural tissue and it may represents an adaptive response to modern urban “environmental abundance”. It is thus proposed that autism is the result of epigenetic disruption in brain development caused by gestational exposure to these conditions (which interfere with neurogenesis). So, it is hypothesized that autism is the physiological and ecological cost that is paid for the enhanced growth rate activation, especially in neural tissue, due to increased resource and energy availability during prenatal and postnatal period of increased plasticity (excess numbers of neurons are produced but they are also liable to impairment). So, an “abundance” phenotype hypothesis for autism may emerge, a holistic approach of childbirth would be possible and well organized preventive programs (about parental health and nutrition before conception, nutrition of pregnant woman and child, optimal breastfeeding, rational use of nutritional supplements, etc) could be carried out.