The purpose of the review article written by Lee,Yamaguchi, and Goto in 2015 is to offer an explanation for the prevalence ofpsychiatric disorders despite the lower fecundity of people diagnosed with psychologicaldisorders with respect to the general population.
They propose that the development of psychiatricdisorders in individuals might be evolutionarily favored in cases of prenatalstress. The authors begin by examininghow certain diseases can be thought of as originating from a discrepancybetween prenatal and postnatal conditions. That is, the prenatal environment could elicit changes in the offspringthat later affect its postnatal health and behavior. This idea is termed the Barkerhypothesis. The authors propose thatthis hypothesis could also apply to neurodevelopmental disorders such asschizophrenia and autism. Since thesedisorders are associated with abnormalities in synaptic connections, the articleexamines the effect of prenatal and postnatal environmental discrepancies onneuronal development. The authors reviewa study completed by Leuba and Rabinowicz in 1979 regarding the development ofdendritic spines in the neurons of mice.
Leuba and Rabinowicz observed that underfed mice usually showed lowernumbers of dendritic spines than mice provided a normal diet duringdevelopment. This relationship wasobserved unless the underfed mice also experienced prenatal conditions in whichnutrients were not abundant. These mice,if raised in a postnatal environment that was again low in nutrients, showednumbers of dendritic spines comparable to mice that were provided a normaldiet. Inthe review article, the authors propose two different results that could occur froma discrepancy between predicted and actual postnatal conditions: adaptive andpreparatory plasticity changes. In whatthe authors termed as an “adaptive plasticity change,” prenatal conditionstriggered adaptive changes during the development of the offspring thatresulted in modified postnatal behavior. Examples of neurodevelopmental disorders which the authors claim mightresult from an “adaptive plasticity change” are autism and attention deficithyperactivity disorder, which develop early in childhood and involve behavioralchanges that could be considered maladaptive or advantageous depending on theoffspring’s postnatal environment. Ifthe postnatal environment predicted during development matched the actualpostnatal environment experienced by the offspring, the authors suggest thatthe behavioral changes observed in these neurodevelopmental disorders would beconsidered beneficial, improving the offspring’s chances of survival.
In what the authors termed as a “preparatoryplasticity change,” prenatal conditions triggered changes in the development ofthe offspring that worked to change postnatal behavior so that the offspring wouldbe prepared for the expected postnatal environment. The authors used the exampleneurodevelopmental disorder of schizophrenia, which develops in early adulthood,to explain how behavioral changes associated with the disorder could beconsidered as merely the result of environmental expectations not meetingreality.In evaluating how genetic factors play a role inpsychiatric disorders, the authors examine the possibility that prenatalchanges induced by stress in the parent could be passed on to his or heroffspring. The authors propose thatthese inherited epigenetic factors, when coupled with mutations or geneticchanges perhaps triggered by the environment, could result in the exhibition ofabnormal behavior. The authors mentionthe work of Crespi, Stead, and Elliot in 2010 which suggested that bothschizophrenia and autism present genetic mistakes that are almost mirror imagesof each other, as if the disorders were on opposite ends of a spectrum. The current review article concludes bystating that neurodevelopmental disorders could be thought of as existing on aspectrum, with contrasting psychiatric disorders at each end and behaviorsconsidered normal in the present environment located in the middle of thespectrum. From an evolutionaryperspective, the development of individuals with psychiatric disorders couldthen be seen as an advantage which improves the survival of the species as a wholeby improving its diversity.